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AQA GCSE Physics Correct Questions And Answers 100%
This type of surface is a good absorber and emitter of thermal radiation Dark, rough (matt) surface This type of surface is a bad absorber and emit... [Show More] ter of thermal radiation Light, shiny surface In this process particles vibrate colliding with each other passing energy along. Solids are best at it, then liquids, then gases. Conduction In this process particles move around carrying energy with them. Gases are best at it, then liquids then solids Convection This process doesn't require a medium (substance) to transfer energy. The energy is carried in the form of waves Radiation Factors affecting the rate of heat transfer 1. Temperature difference to the surroundings 2. Surface area 3. Nature of surface (e.g shiny/matt) The total energy supplied to a device or an appliance. It is often electrical Total Input Energy Energy converted by a device into the form(s) the device was designed for. Useful energy Energy converted by a device into the form(s) the device was NOT designed for. Wasted energy Useful energy transferred by the device divided by total energy input to the device Efficiency Energy cannot be created or destroyed only transformed into other forms The principle of conservation of energy Where does all energy end up eventually? It is transferred to the surroundings, warming them in the process. The unit of energy used in electricity bills kilowatt-hour (kWh) What are the useful and wasted energies transformed by a radio? USEFUL: Sound WASTED: Heat What are the useful and wasted energies transformed by a TV? USEFUL: Sound, Light WASTED: Heat What are the useful and wasted energies transformed by a hairdryer? USEFUL: Heat, Kinetic WASTED: Sound What are the useful and wasted energies transformed by a car? USEFUL: Kinetic WASTED: Heat, Sound The unit of energy normally used (expect in electricity bills) joules (J) Absorption When a wave hits an object and is absorbed the energy of the wave can heat up the object Reflection When a wave 'bounces off' an object Transmission When a wave travels through a material (e.g. visible light through glass) What are the three types of nuclear radiation in order from most to least penetrating? Gamma, Beta, Alpha What are the three types of nuclear radiation in order from most to least ionising (damaging)? Alpha, Beta, Gamma Advantages of Digital over Analogue Digital signals are affected less by interference and can be easily processed by computers. What is an alpha particle? A helium NUCLEUS. What is a beta particle? An electron. Which types of nuclear radiation are deflected by electric and magnetic fields Alpha and Beta (they are always deflected the opposite way to each other) Which particles are found in the small central nucleus of the atom? Protons and Neutrons What is a radioactive substance A substance that gives out radiation from the nuclei of its atoms (no chemical or physical change can stop this happening) Half-life The time it takes for the number of radioactive nuclei in a sample to halve. (or the time it takes for the count rate from a radioactive source to halve). Advantages of Space-based (orbital) telescopes No atmospheric distortion. Can see parts of the spectrum which are absorbed by the atmosphere (UV and X-ray) Disadvantages of Space-based (orbital) telescopes Very expensive to launch and maintain. Advantages of ground based (terrestrial) telescopes Relatively Cheap. Easy to access for repairs and upgrades. Disadvantages of ground based (terrestrial) telescopes Suffer from atmospheric distortion. Can't look at all parts of the EM spectrum (esp. UV and X-ray) What is red shift? The light from distant galaxies appears shifted to the red end of the spectrum suggesting they are moving away from us. The Big Bang Theory The best current theory for how the Universe began, with a giant 'explosion' that created all matter, energy and even space and time itself. Atoms of an element always have the same number of _______ in the nucleus. protons (e.g. all Carbon atoms have 6 protons) Atoms of different isotopes of an element will have different number of _________ in the nucleus. neutrons (e.g. carbon-12 has 6 neutrons, carbon-14 has 8 neutrons). Both have 6 protons. Uses of Alpha Radiation Smoke alarms ( A long half-life source should be used to avoid having to replace it) Dangers of Alpha Radiation An alpha source is very dangerous when swallowed or inhaled as alpha particles cannot normally penetrate the skin. Uses of Beta Radiation Thickness control for paper mills, aluminium foil. ( A long half-life source should be used to avoid having to replace it) Dangers of Beta Radiation Beta sources are dangerous outside the body as beta radiation can penetrate into internal organs. Turbine Part of a power station where high pressure steam rotates the turbine blades Furnace The place where fuel is burned in a fossil fuel power station. The energy released is used to heat water in a boiler. Generator Connected to the turbine. It contains a magnet and wire coils which transform the kinetic into electrical energy [Show Less]
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AQA GCSE Physics -Paper 2 Correctly Answered Questions 100%
Scalar quantities with only magnitude such as speed, distance, time and mass. Vector quantities with a magnitude and direction e.g. acceleration, ... [Show More] force momentum and weight. A vector quantity can be represented as an arrow, the size representing the magnitude and the direction, the direction. Non-contact force the objects are physically separate e.g. magnetism/gravity/electrostatic. 3 non-contact forces magnetism gravity electrostatic Contact force objects are physically touching . 3 contact forces friction resistance tension Gravity Weight is the force acting on an object due to gravity, it acts on an objects 'centre of mass' and is directly proportional to mass Weigh Equation Weight = mass x grav. field strength Resultant forces A number of forces acting on an object may be replaced by a single force that has the same effect as all the original forces acting together, this single force is the called the resultant force. In a tug of war, 1000N to the left and 800N to the right. The resultant force is 200N to the left Free-Body force diagrams When an object is acted on by more than one force you can draw a free-body force diagram to work out the resultant force on the object. It shows the forces acting on an object without any other objects or other forces shown. Each force is shown on the diagram by a vector, which is an arrow pointing in the direction of the force. ( the normal force is that component of the contact force that is perpendicular to the surface that an object contacts) How to resolve forces (force diagram steps) 1. Decide on a scale of N per cm. 2. Draw the 2 given forces, giving respect to their length (more cm if more N) and the angle that you are given 3. Draw a line connecting the end of the 2 other lines to form a triangle 4. Measure the length of this line, then convert it to N by using the scale Relationship between Joules and work done When a force causes and object to move, work is done on the object so when the force causes displacement. One joule of work is done when a force of 1 newton displaces an object 1 metre. 1 Joule = 1 newton-metre. Equation for word done work done = force x distance Elastic Deformation When an elastic object is stretched, bent, twisted or compressed it will return to its original form Inelastic Deformation Polyethene bags will not return to their original shape after being deformed, this is inelastic. Hooke's Law The extension of an elastic object is directly proportional to the force applied as long as the limit of proportionality is not exceeded: Equation for force (Hooke's law) force = spring constant x extention Extension and compression's relationship with elastic potential energy explanation A force that stretches or compresses a spring does work and elastic potential energy is stored in the spring, provided the spring is not elastically deformed, the work done and elastic potential energy are equal. Before the limit of proportionality is breeched the relationship is linear (directly proportional) afterwards it is non-linear Elastic potential energy equation (given) Elastic potential energy = 1/2 x spring constant x extension^2 Moment meaning The turning effect of a force is called its 'moment' Moment equation moment = force x distance Balancing If an object is balanced the clockwise moment is equal to the anticlockwise moment. Levers A lever consists of a load, effort and pivot, levers use moments to multiply a force, they allow a larger force to act on the load that is supplied by the effort. Engine Gears Engine gears have two main jobs, producing torque and speed, however they are inversely proportional so gears are made to make a compromise between the two in any given situation. When starting a car we want high torque, which means being able to carry a greater load , and consequentially less speed. In low gears this is achieved as... 1. The engine causes a small cog on the engine axle to rotate. 2. The small cog on the engine axle is connected to a larger cog on the wheel axle, which increases the torque (moment) exerted. 3.A high turning force but low speed is exerted on the wheel (low gear) When a car is already moving, we want a high speed which is achieved as... 1.The engine causes a larger cog on the engine axle to turn. 2.The larger cog on the engine axle is connected to a smaller cog on the wheel axle, causing a high rate of rotation, but a low turning force. 3. The wheel rotates quickly, causing a high speed Unit for pressure Pressure is a measure of force per unit of area, the si unit is Pascals (Pa) which is one N/m^2 Pressure Equation Pressure = force normal to the surface/area Manometer with oil and water The pressure is equal at each end of the tube, so the less dense oil is higher.(p=hdg)(on sheet) Buoyancy The partially or fully submerged object experiences more pressure at the bottom that on top, this creates a resultant up thrust force called buoyancy. Why objects float An object will rise or float if it is less dense than the substance it is in or if it displaces an amount of the substance that it is floating in greater than it weights, steel ships have a lot of air in them and therefore weigh less than the equivalent amount of water that the ship displaces, so it floats this is because the up thrust from the pressure is greater than the down force of the weight. Atmospheric pressure and how it varies by altitude Air pressure is created by air molecules colliding with a surface, if we consider the density of these particles being same at all attitudes, the fact the volume of the earth's atmosphere increases as we rise in altitude then we can tell that the air pressure will decrease as there is more space for the same amount of particles to bump into each other. Also air is naturally less dense further away from the ground, reducing collisions and therefore pressure. Distance How far an object moved regardless of direction (scalar). Displacement The length of a straight line from the starting point to the finish point with its direction (vector). Walking speed estimate 1.5 m/s Running speed estimate 3 m/s Cycling speed estimate 6 m/s Car speed estimate 13-30 m/s Train speed estimate 50 m/s Aeroplane speed estimate 250 m/s Equation for distance Distance travelled = speed x time Velocity Velocity is a vector quantity representing speed in a certain direction. This means that a circular motion at a constant rate has a constant speed but a constantly changing velocity. Characteristics of a distance-time graph - a flat line means no movement, a change in time but not in distance. - a straight positive line represents a constant movement. - a concave curve represents an acceleration, a convex represents deceleration. - the speed at any point during an acceleration or deceleration can be determined by drawing a tangent Acceleration equation chance in velocity/time Velocity-Time graph characteristics -a flat line means no acceleration, a constant speed. - a straight positive line represents a constant acceleration, concave and exponential acceleration and convex a decreasing acceleration. - no movement is represented by a flat line on the x axis. - the area under the line equals the distance travelled. Terminal velocity explanation Near the Earth's surface any object free falling has an acceleration of 9.8m/s due to gravity. An object falling through a fluid will fall at 9.8m/s until the resultant force (from weight and resistance) is 0 and the object moves at its terminal velocity Process of reaching terminal velocity 1.Accelerates due to weight. 2.Air resistance increases with velocity, weight does not. 3.Air resistance becomes equal to weight, the forces become equal Newton's First Law If a resultant force acting on an object is zero, the object will remain stationary (this is inertia) or if it is moving, it will continue to move at the same velocity. Newton's Second Law The acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to its mass. Resultant force equation Resultant force = mass x acceleration Inertial mass Inertial mass is a measure how difficult it is to change the velocity of an object. It is the ratio of force over acceleration (f=ma rearranged) Newton's Third Law Whenever two objects interact, the forces they exert on each other are equal and opposite. This is explains the result of equilibrium situations. How to find stopping distance stopping distance = thinking distance + braking distance Factors affecting reaction time - tired. - drunk. - high. - driving fast. - influenced by any distractions. Factors affecting breaking distance Breaking distance can be affected by adverse conditions of the road (icy/wet conditions) and/or the vehicle (this is limited to the conditions of the breaks and tyres). How brakes work Breaking distance can be affected by adverse conditions of the road (icy/wet conditions) and/or the vehicle (this is limited to the conditions of the breaks and tyres). A higher speed requires a greater braking force and a greater breaking force means a greater deceleration (this can lead to brakes overheating and loss of control). F=ma shows that if acceleration is high, then force increases, showing that in a car crash with extreme deceleration the force exerted on the victim will be high and therefore dangerous. How to find distance in a collision s=-u^2/2a How to find deceleration in a collision a=-u^2/2s How to find force in a collosion F=m(-u^2/2s) Unit for momentum kg m/s Momentum equation momentum = mass x velocity Conservation of momentum In a closed system the total momentum before an event is equivalent to that after it, this is the conservation of momentum Force equation (using momentum) Force = change in momentum/time Safety features to reduce rate of change of momentum -seat belts -air bags -crumple zones -crash mats -cycle helmets -cushioned grounds in play area Require Practical 6- Force and Extension In the practical, students place known masses on a spring, measure the total resultant length of the spring and calculate its extension. Practical 6 (Extension) Materials • a suitable spring capable of extending more than 1 cm under a load of 1 N with loops at each end • metre ruler • suitable pointer (eg splint and tape) • weight stack appropriate for the spring (eg 10 N in steps of 1 N) • clamp stand • two clamps and bosses • G-clamp or weight to prevent the apparatus tipping over the edge Practical 6 (Extension) Method 1. Set up spring and a ruler on a clamp stand so that the 0mm point is at the bottom of the unextended spring 2.Add masses and then measure the extension 3. Convert the masses to weight with weight=mass x grav. field strength 4.Plot. Should be a straight line. Gradient is 1/spring constant (if force is x and extension is y) Practical 7- Acceleration -the effect of varying the force on the acceleration of an object of constant mass -the effect of varying the mass of an object on the acceleration produced by a constant force Practical 7 (Acceleration) Materials -a 1 m ruler -toy car - bench pulley, string and small weight stack (eg 1 N in steps of 0.2 N) - two clamp stands, clamps and bosses - Blu-Tac or similar to attach weights to the car. Acceleration Practical Method Part 1 (Measuring the effect of force on acceleration at constant mass) 1.Use the ruler to measure intervals on the bench and draw straight lines or place tape across the bench at these intervals. 2.Attach the bench pulley to the end of the bench. 3.Tie a length of string to the toy car or trolley. Pass the string over the pulley and attach the weight stack to the other end of the string. 4.Make sure the string is horizontal and is in line with the toy car or trolley. 5.Hold the toy car or trolley at the start point. 6.Attach the full weight stack (1.0 N) to the end of the string. 7.Release the toy car or trolley at the same time as you start the stopwatch, press the stop watch (lap mode) at each measured interval on the bench and for the final time at 100 cm. 8.Record the results in the table. 9.Repeat steps 5−8 for decreasing weights on the stack for example, 0.8 N, 0.6 N, 0.4 N, 0.2 N. Make sure you place the masses that you remove from the weight stack onto the top of the car each time you decrease the weight. F=ma, a=F/m, a=1/m x F: As force increases, so does acceleration Acceleration Practical Method Part 2 (Measuring the effect of mass on acceleration with a constant force) 1.Setup the bench, pulley, weight stack and car as in steps 1-5 of activity 1 2.Use your results from activity 1 to select a weight for the weight stack that will just accelerate the car along the bench. 3.Put a 200g mass on the car. 4.Hold the car at the start point. 5.Attach your chosen weight stack to the end of the string 6.Release the car at the same time as you start the stopwatch, press the stopwatch (lap mode) at each measured interval on the bench and for the final time at 100 cm. 7.Record the results in a table with distances travelled for each mass 8.Repeat steps 5−8 for increasing more masses on the car F=ma, a=F/m, a=1/m x F: As mass increases, acceleration decreases Action between 2 like poles Repulsion Action between 2 opposite poles Attraction How to test if a substance is magnetic If it repels Characteristics of a permanent magnet •A material that produces its own magnetic field. •Made from ferrous materials or alloys with them (e.g. iron, cobalt, nickel and steel). •Substances that are permanently magnetised and often their alloys are called "magnetically hard". •Alloys with less concentration of the ferrous material are often weaker, temporarily magnetised and therefore magnetically soft. Characteristics of a induced magnet •A material that becomes a magnet when placed in a magnetic field. •It loses most/all its properties instantly after being moved away. •It will always attract to the inducing magnet, as it forms poles opposite to the permanent magnet (e.g. north forms next to south). Characteristics of a magnetic field •The 'non-contact' forces of a magnet are strongest at the poles, like poles repel, unlike attract. The overall strength of the magnetic field depends on the distance from the magnet. •The direction of the magnetic field at any point is given buy the direction of the force that would act on another north pole placed at that point. •The direction of a magnetic field line is always from the north to the South Pole. •A magnetic compass contains a small bar magnet that points towards the earth's magnetic poles which form as if the core were a magnet itself. When a current flows through a conducting wire... a magnetic field is produced around the wire. The strength of the magnetic field depends on: - Size of current. - The distance from the wire. Corkscrew rule The direction of the magnetic field around a current carrying wire follows the direction you turn a corkscrew. Solenoid -A solenoid is a long coil of insulated wire. -Shaping a wire to form a solenoid increases the strength of the magnetic field created by a current through the wire. -The field inside is strong and uniform. Properties of a solenoid -increases in strength as current increases. - reverses if current is reversed. - increases in strength as you get closer to the wire. - increases in strength with an iron core. - outside the solenoid, has a similar shape to a bar magnet. Electromagnet A solenoid with a ferrous metal core. Polarity of Solenoids To work out the north and south end of a Solenoid you look at the end of the solenoid, and see which direction the current is going round. If it is clockwise it is south, if it is going anticlockwise it is north. Motor effect When a conductor carrying a current is placed in a magnetic field (produced by a different magnet), they exert a force on each other called the motor effect. Factors affecting size of force in motor effect -Size of current. - Strength of magnet. - Angle between the wire and the magnetic field lines. The force is greatest when the wire is perpendicular to the magnetic field. There is no force if they are parallel. Fleming's left hand rule Electric motors (motor effect) 1. Coil placed in magnetic field 2. Coil experiences a force, rotating it 3.To keep the coil moving in one direction, a split ring commutator reconnects the two sides of the coil every half-turn Headphones/Speakers 1.a current in the coil creates an electromagnetic field 2.the electromagnetic field interacts with the permanent magnet generating a force, which pushes the cone outwards 3.the current is made to flow in the opposite direction 4.the direction of the electromagnetic field reverses 5.the force on the cone now pulls it back in 6.repeatedly alternating the current direction makes the cone vibrate in and out (the electric current must vary in the same way as the desired sound.) 7.the cone vibrations cause pressure variations in the air, which are sound waves [Show Less]
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Gcse AQA physics Questions and Answers 2022/2023
how is heat transferred from place to place? conduction, convection, radiation What surface is better at absorbing heat? dark matt surfaces ... [Show More] what surface is better at reflecting heat? light shiny surfaces what objects emit infared radiation? all objects. the hotter it is, the more it emits. what does infared radiation involve? waves! not particles what can radition pass through? vaccum particles in solids, liquids and gases have ? amounts of energy different describe the particles in a solid close together particles, with a regular pattern.They vibrate and stay in a fixed position describe the particles in a liquid close particles with a random patter. Move around eachother describe the particles in a gas far apart, random pattern, move quickly and in any direction what is conduction when heat energy moves through a substance are metals, or non metals better conductors metals what are non metals and gases good insulators the hotter the metal is... the more kinetic energy the vibrations have what happens in convection particles with lots of heat energy get less dense and rise, replacing particles with less heat energy. what is it called when a liquid changes to a gas? evaporation what is it called when a gas changes to a liquid condensation what increases condensation rate? increase in temperature of gas what increases rate of evaporation? increase in temperature of liquid, increase surface area, air moving over liquids surface the bigger difference in temperature between object and surroundings... the greater rate of heat energy is transferred small animals have large surface area to volume ratio if small animals have a large surface area to volume ratio they lose heat to surroundings easily and have to eat more to replace energy lost large animals have a small surface area to volume ratio if large animals have a small surface area to volume ratio they lose little heat to surroundings and may risk over heating what enables elephants to cool down quickly large ears lower u-value means better heat insulator what does temperature mean measure of how hot an object is what does heat mean measure of thermal energy contained temperature increase depends on mass of an object, substance it is made from, amount of energy transferred to the obect what are forms of energy magnetic, kinetic, heat, light, gravitational potential, electrical, elastic potential, nuclear what diagram shows the useful and wasted energy sankey diagram what are fossil fuels coal, oil, natural gas what are advantages of fossil fuels they are reliable and quick what are disadvantages of fossil fuels supply is limited, coal and oil release sulphur dioxide, release carbondioxide when burned, increases global warming, what releases the most carbon dioxide, coal or natural gases? coal example of a nuclear fuel uranium, plutonium advantages of nuclear fuels? dont produce sulphur dioxide or carbon dioxide disadvantages of nuclear fuels? non renewable, radioactive material released if there is an accident which would damage health what is wind energy? wind blows into wind turbines, causing them to turn and drive a generator what are the types of water energy? wave, tides, hydroelectric power what is wave energy kinetic energy in waves drive electricity generators what is tide energy tidal barrage is built over a river to make use of kinetic energy in moving water. barrage contains electricity generators which are driven by water rushing through tubes in the barrage what is hydroelectric power? moving water drives electrical generators which are built inside dams advantages of water power? no fuel costs, no harmful gases, reliable, easily switched on disadvantages of water power? hard to produce large amounts of electricity, tidal barrages destroy habitats, hydroelectricity floods farmland, rotting vegetation under water releases methane, a greenhouse gas what is geothermal energy? hot water and steam underground is used to drive turbines how does geothermal energy work in volcanic areas? rocks contain radioactive substances, rocks heat water so it rises to surface naturally, steam and hot water drives turbines and electricity generators how does geotheraml energy work in hot rocks? hot water and steam doesnt rise to the surface, deep wells drilled down to hot rocks and cold water is pumped down to condense the water, hot water rises and can be used to drive turbines and electricity generators advantages of solar energy? renewable, provides energy in remote locations disadvantages of solar energy? inefficient, doesnt work at night how is electricity distributed from power stations to consumers? the national grid what does a step up transformer do steps up voltage what does a step down transformer do decreases the voltage how do you work out the speed of a wave frequency plus wavelength what is a transverse wave? where the vibrations (oscillations) are at right angles to the direction of travel what speed does light travel at, through a vaccum? the same speed what is a longitudinal wave? oscillations are along the same direction as travel what is amplitude the maximum disturbance from undisturbed position what is wavelength length from one chord (bump) to the other what is frequency number of waves produced by a source each second what happens to sound and light waves when they cross a boundary with different densities, e.g air and glass they change speed and change direction what is diffraction when waves meet gap in barrier and they carry on through but more spread out if the gap in diffraction is larger than the wavelength what happens it doesnt spread very much and causes a sharp shadow what happens in diffraction if the gap is similar to the wavelength it causes a lot of spreading with little shadow what waves reflect from surfaces sound and light waves where is the angle of incidence between the incident (incoming ray) and the normal where is the angle of reflection between the reflected ray and the normal what type of echo does a smooth surface produce when a sound wave hits it? strong echo where can waves appear to be coming from? a point beyond the mirror the angle of incidence is the same as the... angle of reflection are sound waves longitudinal or transverse? longitudinal what direction do vibrations occur in? same direction as travel the greater the amplitude of an object... the louder the sound the greater frequency of an object... the higher the pitch what does an object / substance produce when it vibrates? sound what is the electromagnetic spectrum? white light split into prism to form a spectrum what speed do all forms of electromagnetic radiation travel at? the same speed when was the big bang thought to have happened? 13.7 billion years ago what is the big bang theory? origin in all matter of universe was concentrated to a single tiny point and then expanded rapidly into a huge explosion what is the dopplar effect? when a source travels towards you the wavelength decreases and the frequency increases, when a source travels away from you the wavelength increases and the frequency decreases what happens to the source in the dopplar effect when it moves away from you the wavelength increases and the frequency decreases what direction are distant galaxies moving from us? away from us the further away a galaxy is... the faster it is moving what does CMBR mean? microwaves coming from every direction in space [Show Less]
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AQA A-Level Physics Correct Questions and Answers 2023
Rest Mass of Proton in eV and MeV 938 x 10^-6 eV and 938MeV Rest Mass of Electron in eV and MeV 0.51 x 10^-6 and 0.51MeV Definition of Isot... [Show More] ope Same Proton Number and Different Nucleon Number Mass of Proton/Neutron and Electron 1.67x10^-27 and 9.11x10^-31 Specific Charge Equation Charge of Proton x Amount of Protons/Mass of Amount of Nucleons - Charge/Mass Definition of Strong Nuclear Force Attractive Force - Holds Protons and Neutrons Together in Nucleus What Range Does The Strong Nuclear Force Effect 0.5 up to 3-4 Femtometres (fm) Effect of Strong Nuclear Force Less Than 0.5fm Repulsive to Prevent Protons and Neutrons Being Pushed Into Each Other What Force Has a Limited Range (Distance) Strong Nuclear Force Nucleon and Proton Number of Alpha Radiation 4 Nucleons, 2 Proton Number Nucleon and Proton Number of Beta Radiation 0 Nucleons, -1 Proton Number Definition of Electromagnetic Wave A Burst of a Packet of Photons Equation for Photon Energy E = hf Equation for Power of a Beam Power of Beam = nhf What is Annihilation? Two Particles Collide to Form 2 Photons What is Pair Production? Photon Creates a Particle and Anti-Particle Annihilation Equation for Minimum Energy of Photon hf_min = Eo Pair Production Equation for Minimum Energy of Photon hf_min = 2Eo Feynman Diagram for Neutron-Neutrino Interaction Feynman Diagram for Proton-Antineutrino Interaction Feynman Diagram for B- Decay Feynman Diagram for B+ Decay Feynman Diagram for Electron Capture What Force Do Hadrons Interact With? Strong Interaction What Force Do Leptons Interact With? Weak Interaction State The Charge of Up, Down and Strange Quarks 2/3, -1/3, -1/3 State The Charge of Anti Up, Down and Strange Quarks -2/3, 1/3, 1/3 Quark Composition of Proton uud Quark Composition of Neutron udd Quark Composition of K+ and K- u_s, s_u Quark Composition of Pie+ and Pie- u_d, d_u Conservation Laws - What is Conserved? Conserved: Charge, Momentum, Baryon Number, Energy and Lepton Number Conservation Laws for Strangeness? Only Conserved in Strong Interactions Definition of Threshold Frequency Minimum Frequency of Light That Can Cause The Photoelectric Effect to Take Place What is The Correlation Between Number of Electrons Emitted and Intensity of Radiation These Are Proportional Equation for Energy of a Photon (2 Equations) E = hf or hc/ ,\ Definition of Work Function The Minimum Energy Need by an Electron to Leave a Metal Surface Equation for Maximum Kinetic Energy of an Electron Ek_max = hf - o (work function) Equation for Threshold Frequency F = o/h Definition for Excitation Atom Absorbs Energy Because of an Electron Moving From an Inner to an Outer Shell Definition for Ionisation Where an Atom Takes in or Release Electrons to Form Positive/Negative Ions Equation for Energy of An Emitted Photon E = hf = E1 - E2 Process of Fluorescense (Fluorescent Tube) - Ionisation and Excitation of Mercury Atoms Occur as They Collide With Electrons Which Have Been Accelerated - The Mercury Atoms Emit UV Photons and Photons of Much Less Energy - The UV Photons are Absorbed by Atoms in the Fluorescent Coating Causing Excitation of the Atoms - These Atoms De-Excite in Steps and Emit Visible Light Photons Definition of Wave-Particule Duality With Example Matter Particles Have Wave-Like Natures and Particle-Like Natures, E.g Photons Equation for De-Broglies Wavelength (2 Equations) ,\ = h/p or h/mv [Show Less]
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AQA Physics GCSE Questions And Answers 2022/2023
What is the radius of an atom? Around 10^-10m What is the basic structure of an atom? A positively charged nucleus composed of both protons and ne... [Show More] utrons surrounded by negatively charged electrons What fraction of the atom is the radius of the nucleus? 1/10,000th Most of the mass of an atom... ...is concentrated in the nucleus How can electron arrangements change in an atom? 1. Absorption of electromagnetic radiation - move further from nucleus; higher energy level 2. Emission of electromagnetic radiation - closer to nucleus; lower energy level The number of protons in an atom is equal to... ...the number of electrons in the atom What do all atoms of the same element have in common? They have the same number of protons Mass number The total number of protons and neutrons How can atoms be represented? Mass number on top, atomic number under What happens if atoms lose one or more outer electrons? They turn into positive ions Isotope An atom of the same element with a different number of neutrons What may lead to a scientific model being changed or replaced? New scientific evidence How has the atomic model developed? 1. Tiny undivisible spheres 2. Plum pudding model 3. Nuclear model 4. Bohr's nuclear model 5. Discovery of protons 6. Discovery of neutrons Plum pudding model The atom is a ball of positive charge with negative electrons embedded in it Nuclear model (alpha scattering experiment) 1. Most particles went straight through - mostly empty space, nucleus small compared to whole atom 2. Some particles deflected several degrees - nucleus positively charged as positive particles were repelled 3. A few particles deflected almost 180 degrees - nucleus contains most of the mass of the atom Conclusion: the mass of the atom is concentrated at the centre (nucleus) and the nucleus is charged Niels Bohr's nuclear model Electrons orbit the nucleus at specific distances - his theoretical calculations agreed with experimental observations Proton discovered Later experiments led to the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles which each had the same amount of positive charge Neutrons discovered The experimental work of James Chadwick provided the evidence to show the existence of neutrons How long after the nucleus became an accepted scientific idea were neutrons discovered? 20 years Radioactive decay A random process in which an unstable atomic nucleus give out radiation as it changes to become more stable Activity The rate at which a source of unstable nuclei decays, measured in bequerel (Bq) Count-rate The number of decays recorded each second by a detector (eg Geiger-Muller tube) Alpha particle Two neutrons and two protons, the same as a helium nucleus Beta particle A high speed electron ejected from the nucleus as a neutron turns into a proton Gamma ray Electromagentic radiation from the nucleus What are the 4 types of nuclear radiation? Alpha particle, beta particle, gamma ray, neutron Alpha radiation - absorber materials, range in air, ionising power 1. Thin sheet of paper 2. About 5cm 3. Most ionising power Beta radiation - absorber materials, range in air, ionising power 1. Aluminium sheet (5mm), lead sheet (2 - 3mm) 2. 1m 3. Medium ionising power Gamma radiation - absorber materials, range in air, ionising power 1. Thick lead sheet (several cm), concrete (more than 1m) 2. Long range - spreads in air without being absorbed 3. Least ionising power Which radiation is used in smoke alarms and why? Alpha radiation - ionises the air so there is a current; smoke causes a drop in current, triggering the alarm Beta and gamma radiation do not have enough ionising power to make the air conduct electricity Which radiation is used in metal foil production and why? Beta radiation - detector measure radiation passing through foil; if the foil is too thick, the detector reading drops Alpha would be stopped by the foil, gamma would pass through the foil unaffected The emission of the different types of nuclear radiation may cause... ...a change in mass and/or the charge of the nucleus Radioactive decay is... ...random Half-life (2) 1. The time it takes for the number of nuclei in a sample for halve 2. The time it takes for the count rate/activity from a sample containing the isotope to fall to half its initial level Equation for the final count rate (remaining number of unstable nuclei) count rate (number of unstable nuclei after n half lives) = initial count rate (number of unstable nuclei)/2^n Radioactive contamination The unwanted presence of materials containing radioactive atoms on other materials What is the hazard of contamination from? The decay of the contaminating atoms What effects the level of hazard? The type of radiation emitted Irradiation The process of exposing an object to nuclear radiation; the irradiated object does not become radioactive Why is radiation dangerous? Radiation causes ionisation which can damage or kill the cell, causing mutations and possibly cancer How can workers reduce their exposure to ionising radiation? (3) 1. Keep as far away from source of radiation -e.g. by using special handling tools with long handles 2. Spend as little time as possible in at-risk areas 3. Shield themselves by staying behind thick concrete barriers and/or using thick lead plates Why is it important for the findings of studies into the effects of radiation on humans to be published and shared with other scientists? So that the findings can be checked by peer review Background radiation is around us... ...all the time What 2 sources does background radiation come from? 1. Natural sources such as rocks, cosmic rays from space 2. Man-made sources such as the fallout from nuclear weapons testing and nuclear accidents What may the level of background radiation and radiation dose be affected by? occupation and/or location sieverts (Sv) The unit of radiation dose (do not need to recall for exam) 1000 millisieverts (mSv) = 1 sivert (Sv) Radioactive isotopes have a ... range of half-life values very wide Why do hazards associated with radioactive materials differ according to their half life? (2) 1. Materials with a longer half life have the potential to be more dangerous as they will be emitting radiation for a long time 2. For example iodine, which emits gamma radiation, is used as a medical tracer as it has a half life of 8 days - lasts long enough for test but decays into a stable product after a few weeks so radiation does not kill cells What are nuclear radiations used in medicine for? (2) 1. Exploration of internal organs. 2. Control or destruction of unwanted tissues Describe the 4 uses of nuclear radiation 1. Iodine tracers 2. Gamma cameras 3. Beams of gamma radiation to cause cancerous tumours 4 Radioactive implants to destroy cancer cells Describe the use of nuclear radiation to explore internal organs - iodine 1. Tracers are used to track the flow of a substance through an organ 2. Patient drinks water containing radioactive iodine. For a blocked kidney the count rate reading stays up as the iodine stays in the kidney 3. Iodine is used for this as it has a half life of 8 days (long enough for test, but decays after a few weeks), emits gamma radiation (can be detected outside body) and decays into a stable product Describe the use of nuclear radiation to explore internal organs - gamma cameras 1. Patient injected with a solution containing a gamma-emitting radioactive isotope which is absorbed by the organ 2. Detector signals are used to build up an image of where the isotope is located in the organ 3. Isotope must be a gamma emitter with a long enough half life to give useful image, but short enough so that it is mostly decayed after picture Describe the use of nuclear radiation to control and destroy unwanted tissue - beams of gamma 1. Gamma radiation in a beam destroys cancerous tumours 2. Isotope of cobalt with 5 year half life 3. Gamma is used as it can penetrate deeper into the body Describe the use of nuclear radiation to control and destroy unwanted tissue - radioactive implants 1. Small seed/rod implants irradiate tumour 2. Beta or gamma radiation 3. Half lives long enough to irradiate tumour over a given time, but short enough that most of the nuclear will decay soon after Risks of using radiation to treat patients Radiation can ionise both healthy and cancerous cells, causing the patient to feel ill Nuclear fusion and fission don't forget to revise this if you're doing triple science!! (sorry I ran out of time to make it) What is nuclear fusion? The splitting of a large and unstable nucleus (e.g. uranium or plutonium) What must usually happen for fission to occur and why? Usually the unstable nucleus must first absorb a neutron as spontaneous fission is rare Describe what happens in a fission reaction 1. Nucleus splits into 2 smaller nuclei roughly equal in size 2. Emits 2 or 3 neutrons plus gamma rays 3. Energy is released What do all of the fission products have? Kinetic energy What may happen to the neutrons? They may go on to start a chain reaction What is controlled in a nuclear reactor and why? The chain reaction is controlled in a nuclear reactor to control the energy released How are chain reactions controlled in a nuclear reactor? 1. Water acts as a moderator to slow down fission neutrons 2. Control rods whose depths can be adjusted absorb surplus neutrons Why is there an explosion caused by a nuclear weapon? Due to an uncontrolled chain reaction Nuclear fission diagram Draw at least 2 levels! with e neutrons emittes b What is nuclear fusion? Nuclear fusion is the joining of 2 light nuclei to form a heavier nucleus. In this process some of the mass may be converted into the energy of radiation. [Show Less]
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AQA Physics Correct Questions And Answers 2023
Energy is transferred between stores Thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic, nuclear Energ... [Show More] y is transferred... Mechanically (by a force doing work), electrically (work done by moving charges), by heating or by radiation (like light or sound) When a system changes, energy is transferred It can be transferred into or away from the system, between objects in the system or between different types of energy stores. Closed systems are where neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always 0 kinetic energy energy of motion - the greater an object's mass and the faster it is going, the more energy there will be in its kinetic energy store. Ek (j) = 1/2m(kg)v(m/s) squared Raised objects store energy in gravitational potential energy stores lifting an object in a gravitational field requires work, causing an energy transfer to the the GPE store of the object. Ep(j) = m(kg)g(n/kg)h(m) Falling objects transfer energy Falling objects transfer energy from its GPE store to its kinetic energy store. When there's no air resistance, energy lost from the GPE store = energy gained in the kinetic energy store Stretching transfers energy to elastic potential energy stores As long as the limit of proportionality has not been exceeded, Ee (j) = 1/2 k (N/m) e (m) squared specific heat capacity the energy required to raise the temperature of one gram of a substance by one degree Celsius. 🔼E (j) = m(kg) c(j/kgdegree) 🔼theta (degrees Celsius) Conservation of energy principle Energy can be transferred but can never be created of destroyed Dissipated energy energy used up in a system, typically lost due to work done by friction, 'wasted energy' Phone energy When you use the phone, energy is usefully transferred from the chemical energy store of the battery in the phone, but some of this energy is dissipated to thermal energy Closed system energy transfer A cold spoon is dropped into hot soup in an insulated flask, which is then sealed. Energy is transferred from the thermal energy store of the soup to the useless thermal energy of the spoon Power The rate at which work is done (watts). P(w) = E(j) / t(s) Powerful machine One which transfers a lot of energy in a short space of time Conduction occurs mainly in solids Conduction is the process where vibrating particles transfer energy to neighbouring particles. Long definition of conduction Energy transferred to an object by heating is transferred to the thermal store, which is shared across the kinetic store of the particles. The particles' collisions cause energy to be transferred between particles kinetic energy stores. thermal conductivity the Mrs sure of the rate at which thermal energy can travel through a material Convection occurs only in liquids and gases Convection is where energetic particles move away from hotter to cooler regions Convection longer definition Unlike in solids, the particles in liquids and gases are able to move. When you heat a region of a gas/liquid, the particles move faster and the space between particles increases. This causes the density of the region to decrease. Because they can flow, the warmer and less dense region will rise above denser cooler regions. If there is a constant heat source, a convection current will be made Radiators - convection currents Energy is transferred from the radiator to nearby air particles by conduction. The air by the radiator becomes warmer and less dense. This warm air rises and is replaced by cooler air. At the same time, the previously heated air transfers energy to the surrounding and cools, becomes denser, and sinks. This cycle repeats and causes a flow of air to circulate around the room How to reduce unwanted energy transfers Lubrication and thermal insulation Lubrication reduces frictional forces When something moves, there's at least one frictional force acting on it, causing some energy to be dissipated. For objects that are rubbed together, lubricants reduce the fiction between the object's surfaces when moved. Lubricants tend to be liquids (like oil) to flow easily between objects and coat them Insulation reduces the rate of energy transfer by heating Things to do to prevent energy loss through heating... - have think walls made from low thermal conductivity material. This makes the rate of energy transfer slower, so the building will cool more slowly. - use thermal insulation Thermal insulation examples - cavity walls made of an inner and outer wall with an air gap in between to reduce the amount of energy transferred by conduction. - loft insulation can reduce convection currents created in lofts - double glazed windows have an air gap between two layers of glass to prevent energy transfer by conduction - draught excluders around doors and windows reduce energy transfers by convection Most energy transfers involve some waste energy Efficiency = useful output energy transfer / total input energy transfer OR efficiency = useful power output / total power input Non renewable energy resources will one day run out Fossil fuels and nuclear fuels. Fossil fuels are typically burnt to provide coal, oil, and natural gas. They damage the environment but provide most of our energy Renewable energy resources will never run out These are: the sun, wind, water waves, hydro-electricity, bio-fuel, tides, geothermal. Most of them do damage to the environment, but in less nasty ways than non renewables. However, they don't provide much energy and some are unreliable as they depend on the weather Energy resources can be used for transport Non renewable - petrol and diesel powered vehicles use fuel from oil. Coal can be used in old fashioned steam trains to boil water for steam. Renewable - vehicles running on bio-fuels or a mix of a bio-fuel and petrol/diesel. Electricity sometimes powers vehicles and can be generated using renewable or non renewable resources Energy resources can also be used for heating Non renewable - natural gas is widely used for heating homes. The gas heats water, which gets pumped into radiators. Coal is commonly burnt in fireplaces. Electric heaters use electricity generated from non renewable resources. Renewable - a geothermal heat pump uses geothermal energy resources to heat buildings. Solar water heaters use to the sun to heat water, which gets pumped into radiators. Wind power This involves putting up lots of wind turbines in an exposed place, like on coasts. The turbines have a generator inside them - the rotating blades turn the generator to produce electricity. wind power advantages There's limited pollution (only when they're first manufactured), no fuel costs and minimal running costs, no permanent damage to the landscape wind power disadvantages They spoil the view, very noisy, unreliable as they depend on the weather, initial costs are quite high Solar cells They generate electric currents from the sun. They are often the best energy source to charge calculator or watch batteries, as they don't use much electricity. solar power advantages There's no pollution (although they use a lot of energy to manufacture), reliable in sunny countries in the daytime, energy is free and running cost extremely low solar power disadvantages Unreliable because they depend on weather, can't increase power output when there is extra demand, initial costs are high school Geothermal power This is energy in underground thermal energy stores. It is possible in volcanic areas or where hot rocks lie close to the surface. The source of a lot of this energy is the slow decay of various radioactive elements deep inside the earth Geothermal power advantages Free energy that is reliable and does very little damage to the environment. Can be used to generate electricity or heat buildings Geothermal power disadvantages There aren't many suitable locations for power plants, and the cost of building a power plant is high compared to the amount of energy that it produces hydroelectric power used falling water It tends to require the flooding of a valley by building a dam. Water is allowed out through turbines Hydro-electric power advantages There is no pollution and it can provide an immediate response to an increased demand for electricity. It is reliable and there are no fuel costs and minimal running costs Hydro-electric power disadvantages There is a big environmental impact from the valley flooding (rotting vegetation releases methane and CO2) and loss of habitat for some species. Initial costs are high Water power Lots of small wave-powered turbines around the coast. The moving turbines are connected to a generator Water power advantages There is no pollution, no fuel costs and minimal running costs. Can be useful on small islands Water power disadvantages It disturbs the seabed and the marine animals' haibitats. Spoils the view, hazard to boats, fairly unreliable, initial costs are high Tidal barrages Tidal barrages are big dams across river estuaries, with turbines in them. As the tide comes in the estuary gets filled up. The water is then allowed out through turbines at a controlled speed. Tides are produced by the gravitational pull of the moon and sun Tidal barrages advantages There is no pollution, pretty reliable as they always happen twice a day, no fuel floats and minimal running costs Tidal barrages disadvantages It prevents free access for boats. Spoils the view, and alters habitat, the height of the tide is variable, initial costs are moderately high Bio-fuels These are renewable energy resources created from plant products or animal dung. They can be solid, liquid, or gas and can be burnt to produce electricity or run cars in a similar way to fossil fuels Biofuel advantages They are fairly reliable as crops take a relatively short time to grow and some crops can grow all year round. Biofuel disadvantages They can't respond to immediate energy demands - to combat this, biofuels are continuously produces and stored. The cost to refine them is very high. Sometimes large areas of forest have been cleared for room to grow bio-fuels, resulting in species losing their natural habitats. The decay and burning of this vegetation increases CO2 and Meghan emissions Non-renewable resources are reliable There is enough fossil and nuclear fuels to meet current demand, and are extracted from the earth fast enough that power plants always have fuel, meaning they can respond quickly to demand. However, they are slowly running out. While the set up costs of power plants is high, the running costs aren't expensive. nonrenewable resources create environmental problems Coal, oil, and gas release CO2 when burned which adds to the greenhouse effect and contributes to global warming. Burning coal and oil release sulfur dioxide, leading to acid rain. Power plants spoil view. Oil spillage cause serious environmental problems, affecting animals. Currently we still depend on fossil fuels In the 20th century, The electricity use of the uk massively increased as the population grew. Since the start of the 21st century, it is slowly decreasing as we get better at being more efficient and careful. Most of our electricity is produced using fossil fuels. We are trying to increase our use of renewable energy resources. This move to renewable energy has been triggered by... People want to use more renewable energy resources We went to do less harm to the environment as we are aware of the consequences. We are aware non renewables will one day run out. Car companies have been affected by this change in attitude. Electric cared and hybrids are already being sold and their popularity is growing The use of renewables is limited by reliability, money, and politics Although scientists can advise, they don't have the power to make people change their behaviour. Building renewable power plants is expensive and so some energy providers are reluctant to do this. They might not be reliable , meaning more research would have to be done. Making personal changes can be expensive - hybrid cars are expensive as are solar panels Charge flow = Current x time What is current The flow of electric charge (amps) What is resistance Any thing that slows the flow down What is pd (or voltage) The driving force behind the charge Potential difference = Current x resistance What measures current An ammeter put in series What measures pd A voltmeter put in parralell What does an ohmic conductor have What does a phillament lamp IV characteristic graph look like What does a diode IV characteristic graph look like When is resistance highest in LDRs Dark places When is resistance highest in Thermistors In cold What happens to potential difference in a series circuit Is is shared V=v1+v2 etc What happens to current in a series circuit It is the same What happens to resistance in a series circuit Resistance adds up What happens to potential difference in parallel circuits It is the same What happens to current in a parralell circuit It is shared What happens to resistors in a parralell circuit It reduces the total resistance total resistance of 2 resistors is less than the smallest individual resistor What is mains supply Ac (p+n ends alternate) 230v, 50hz What is the blue wire Neutral What is the red wire Live, provides ac What is the green and yellow wire Earth wire When charge flows in a circuit... ... work is done Energy transferred = Power x time Charge flow (c) x PD Power= Pd x Current Current^2 x resistance J/time National grid uses High PD low current so less energy lost to surroundings. This is charged by step up and step down transformers What is the national grid System of cables and transformers that cover the uk and connects power stations to consumers What is battery supply Dc Build up of static is caused by Friction, negative electrons are scraped off What does too much static cause Sparks. High PD -> strong electrical field -> electrons to be removed -> current flows through air -> spark Electric field lines go From positive to negative Charged objects in an electric field Feel a force What does a diode look like? What does a resistor look like? What does a variable resistor look like? What does a LED look like? What does a fuse look like? What does a thermistor look like? What does a LDR look like? for a circuit to work.... it must have a source of potential difference How do objects become charged with static electricity? when certain insulating materials are rubbed against each other, - particles move from one to the other. How does sparking happen? electrical charge builds on the object and if the PD is large enough(large PD, strong electric field) , electrons jump across, this is a spark. What happens to like and opposite charges? like charges repel, opposites attract Explain the concept of an electric field? a charged object creates an electrical field around itself. the electric field is strongest close to the charged object. What does the electric field of a + and - particle look like when a second item is added in the field... it feels a force (attraction or repulsion) the further away, the weaker the force. define density it is a mass of an object per unit volume what is the formula for density? desnity (kg/m3) = mass (kg) / volume (m3) 1 g/cm3 = 1000 kg/m3 what does the density of an object depend on? what it is made of and how its particles are arranged how are the particles arranged in a dense material? its particles are packed tightly together. the particles in a less dense material are more spread out - if you compressed the material, its particles would move closer together, and it would become dense what changes when you compress a material? the mass does not change, it is only the volume that decreases what are the three states of matter? solid, liquid, and gas. the particles of a substance in each state are the same - only the arrangement and energy of the particles are different S O L I D S strong forces of attraction hold the particles close together in a fixed, regular arrangement. the particles don't have much energy so they can only vibrate about their fixed positions. the density is generally highest in this state as the particles are closest together L I Q U I D S there are weaker forces of attraction between the particles. the particles are close together, but can move past each other, and form irregular arrangements. they have more energy than the particles in a solid - they move in random directions at low speeds. liquids are generally less dense than solids G A S E S there are almost no forces of attraction between the particles. the particles have more energy than in liquids and solids - they're free to move, and travel in random directions at high speeds. gases are generally less dense than liquids - they have low densities method for finding the density of regular objects use a ruler to measure the volume - lxwxh - and then record your results into a table, convert cm into m by the volume times 10-6, measure the mass with a mass balance, convert g into kg by dividing by 1000 and then record results, calculate the density by doing mass/volume method for finding the density of irregular objects measure the mass of the object with a mass balance and convert g into kg, fill the Eureka beaker with water up to just below the hole where the water will flow out of once an object is placed inside, place the object inside the Eureka beaker and wait until the water has stopped dripping into the measuring cylinder - this is the volume, calculate the density disadvantages of a mass balance (required practical) may have forgotten to press the clear button first before placing items onto the balance, breathing onto the balance, simplified the number disadvantages of the Eureka beaker and measuring cylinder (required practical) didn't always wait until all of the water had dripped out of beaker, inaccurate reading from the measuring cylinder inaccuracy in the actual density (required practical) rounded the numbers to one or two decimal points because we couldn't the whole number into the table which makes our results less reliable why do particles in a system vibrate or move around? because they have energy in their kinetic energy store, and potential energy store due to their positions how is the energy stored in a system? by its particles. the internal energy of a system is the total energy that its particles have in their kinetic and potential energy stores what effects occurs when heating an object? the heat energy is transferred to the object's particles where they gain energy in their kinetic stores and move faster, increasing the internal energy what effect does heat make on the temperature of an object? it leads to a change in temperature or a change in state. if the temperature changes, the size of the change depends on the mass of the substance, specific heat capacity, and the energy input formula of specific heat capacity change in thermal energy = mass x SHC x temperature change what shows that a system has high specific capacity? materials that need to gain lots of energy in their thermal energy stores to warm up also shows that they can store a lot of energy in their particles before running out of space to store the thermal energy define specific heat capacity it is the amount of energy needed to raise the temperature of 1 kg of a substance by 1 degrees celsius when does a change in state occur? if the substance is heated enough - the particles will have enough energy in their kinetic energy stores to break the bonds holding them together what happens when you heat a liquid? it turns into a gas - a change in state what happens when you heat a solid? it melts and becomes a liquid - a change in state what happens to the particles when cooling occurs in systems? the particles lose energy and form bonds. what does a solid look like? the particles are all in a pack together in a fixed position, however, they are also vibrating - the vibration increases as the temperature increases. what does a liquid look like? the particles are still close together, however they are not in a fixed position. they are vibrating and moving in random directions at low speeds what does a gas look like? the particles are now all spaced out and are moving in random directions at high speeds. there are hardly no bonds so this means you can compress a gas, unlike with a solid or a liquid because their particles still have bonds what type of change is a change in state? a physical change, which means that you don't end up with a new substance but it is in a different form what is the key word for the number of particles that doesn't change? mass is conserved why do we see flat spots on heating graphs? because these are the moments where the heat energy being transferred isn't being used to raise the temperature, instead it is breaking intermolecular bonds what happens to the bonds when a substance is condensing or freezing? bonds are forming between particles, which releases energy. this means that the internal energy decreases, but the temperature doesn't go down until all the substance has turned to liquid or a solid what is the specific latent heat of a substance? the amount of energy needed to change 1 kg of it from one state to another without changing its temperature what is specific latent heat for cooling? the energy released by a change in state what is the name for the specific latent heat for changing between a solid and a liquid? specific latent heat of fusion what is the name for the specific latent heat for changing between a liquid and a gas? specific latent heat of vaporisation what is the formula for specific latent heat? energy / mass what are the units used in the formula for specific latent heat? energy (joules), mass (kg), specific latent heat (j/kg) in which directions are the particles in a gas moving? they are moving in random directions and speeds. if you increase the temperature of a gas, you transfer energy into the kinetic energy stores of its particles what happens if you increase the temperature for the particles of a gas? the average energy and the average speed of its particles increases. this is because the energy in the particles' kinetic energy stores is 1/2mv2 what happens when gas particles collide into each other? they exert a force and a pressure on it. in a sealed container, the outward gas pressure is the total force exerted by all of the particles in the gas on a unit area of the container walls what do faster particles and more frequent collisions lead to? an increase in net force, and so gas pressure. increasing the temperature will increase the speed, and so the pressure, if volume is kept constant alternatively, what happens if temperature is constant? increasing the volume of a gas means the particles get more spread out and hit the walls of the container less often. the gas pressure decreases fill in the blank: pressure and volume are ......... proportional inversely what does it mean if volume and pressure are inversely proportional? when volume goes up, pressure goes down what is the formula for when gas of fixed mass is at a constant temperature? pV = constant what are the units for the formula pV = constant? pressure (Pa), volume (m3) what does the pressure of the gas cause? a net outwards force at right angles to the surface of its container [Show Less]
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AQA A level Physics Questions and Answers
Acceleration The rate of change of velocity Accurate result A result that is close to the true answer Apha decay A type of decay in which ... [Show More] an unstable nucleus of an atom emits an alpha particle Alternating current A current that changes with time in a regular cycle Ammeter A component used to measure the current flowing through a circuit Amplitude The maximum displacement of a wave Angle of incidence The angle that incoming light makes to the normal or a boundry Angle of refraction The angle that incoming light makes to the normal of a boundary Annihilation The process by which a particle and its antiparticle meet and their mass gets converted to energy in the form of a pair of gamma ray photons Anomalous result A result that doesn't fit in with the pattern of the other results in a set of data Antimatter The name given to all antiparticles Antineutrino The antiparticle of a neutrino Antiparticle A particle with the same rest mass and energy as its corresponding particle but equal and opposite charge Atom A particle made up of protons and neutrons in a central nucleus and electrons orbiting the nucleus Atomic number The number of protons in an atom of an element Baryon A type of hardon made up of three quarks Baryon number The number of baryons in a particle Beta-minus decay A type of decay in which an unstable nucleus of an atom emits a beta-minus particle (an electron) and an antineutrino Breaking stress The lowest stress that is big enough to break a material Brittle A brittle material doesn't deform plastically but snaps when the stress on it reaches a certain point ` Brittle fracture When a stress app;lied to a brittle material causes tiny cracks at the materials surface to get bigger until the material breaks completely Categoric data Data that can be sorted into categories Center of mass The point which you can consider all of an object's weight to act through Circuit symbol A pictorial representation of an electrical component Coherent Sources that have the same wavelength and frequency and a fixed phase difference between them are coherent Compressive force A force which squashes something Constructive interface When two waves interfere to make a wave with a larger displacement Coulomb A unit of charge. One coulomb is the amount of charge that passes in one second when the current is one ampere Couple A pair of forces of equal size which act parallel to each other but in opposite directions Critical angle The angle of incidence at which the angle of refraction in 90 degrees Current The rate of flow of charge in a circuit, measures in amperes Continuous data Data that can have any value on a scale Density The mass per unit volume of a material or object Dependent variable The cariable that you measure in an experiment Destructive interference When two waves interfere to make a wave with a reduced displacement Diffraction When waves spread out as they pass through a narrow gap or go round obstacles Diffraction grating A slide or other thin object that contains lots of equally spaced slits very close together, used to show diffraction patterns of waves Diode A component designed to allow current flow in one direction only. Directly proportional A change in ove variable results in a change in the other variable, the changes are always related by the same constant Discrete data Data that can only take certain values Displacement How far an object has traveled from its starting point in a given direction in the case of a wave, it is the distance a point on a wave has moved from its undisturbed position Drag Friction caused by a fluid (gas or liquid) Efficiency The ratio of useful energy given out by a machine to the amount of energy put into the machine Elastic An elastic material returns to its original shape/length once the forces acting on it are removed Elastic limit The force beyond which a material will be permanently stretched Elastic strain energy The energy stored in a stretched material Electromagnetic force A fundamental force that causes interactions between charged particles. Virtual photons are the exchange particle Electromagnetic spectrum A continuous spectrum of all the possible frequencies of electromagnetic radiation Electromotive force (E.M.F) The amount of electrical energy a power supply transfers to each coulomb of charge Electron A lepton with a relative charge of -1 and a relative mass of 0.0005. Electron capture The process of a proton rich nucleus capturing an electron to turn a proton into a neutron, emitting a neutrino Electron proton collision The process of an electron colliding with a proton and producing a neutron and a neutrino Electron volt The kinetic energy carried by an electron after it has been accelerated through a potential difference of one volt Equilibrium An object is in equilibrium if all the forces acting on it cancel each other out Exchange particle A virtual particle which allows forces to act in a particle interaction Excitation The movement of an electron to a higher energy level in an atom Fernman diagram A diagram used to represent particle ineraction First order line The first line either side of the zero order line in a diffraction grating interference pattern First overtone A resonant frequency of a stationary wave for which the wavelength is the length of the string Free fall The potion of an object undergoing an acceleration of g Frequency The number of whole wave cycles (oscillations) per seconds passing a given point, Or the number of whole wave cycles given out from a source per second. Friction A force that opposes motion. It acts in the opposite direction to the motion. It arises when two objects are moving past each other, or an object is moving througha fluid. Fundamental frequency A resonant frequency of a stationsry wave for which the wavelength is double the length of the string Fundamental particle A particle which cannot be split up into smaller particles Gravitational force A fundamental force which causes attraction between objects with a force proportional to their mass Gravitational potential energy The energy an object gains when lifted up Ground state The lowest energy level of an atom Hadron A particle that is affected by the strong nuclear force Hooke's law The extension of a stretched object is proportional to the load or force applied to it, up to the limit of proportionality. Hooke's law limit The point beyond which force is no longer proportional to extension. Also known as the limit of proportionality Hypothesis A specific testable statement based on a theory about what will happen in a test situation Independent variable The variable that you change in an experiment Interference The superposition of two or more waves Internal resistance The resistance created in a power source when the electrons collide with atoms inside the power source Ionisation The process where an electron is removed from to an atom Ionisation energy The energy required to remove an electron from an atom Isotope An isotope of an element has the same proton number as the element but a different nucleon number I-V characteristic A graph which shows how to current flowing through a component changes as the potential difference across it is increased Kinetic energy the energy possessed by a moving object Lepton A fundamental particle that is not affected by the strong nuclear force Lepton number The number of leptons in a particle, the lepton number is counted separately for different types of leptons Level A structure with a rigid object and a pivot in which an effort force works against a load force Light-dependent resistor A resistor with a resistance that depends on the intensity of light falling on it. The resistance decreases with increasing light intensity Limit of proportionality The point beyond which force is no longer proportional to extension. Line spectrum The pattern of lines produced by photons being emitted or absorbed by electrons moving between energy levels in an atom Line absorbtion spectrum A light spectrum with dark lines corresponding to different wavelengths of light that have been absorbed Line emission spectrum A spectrum of bright lines on a dark background corresponding to different wavelengths of light that have been emitted from a light source Longitudinal wave A wave in which the vibrations are in the direction of travel of the wave Lost volts The energy wasted per coulomb overcoming the internal resistance of a power source Mass The amount of matter in an object Mass number The number of nucleons in an atom of an element Matter The name given to all particles Maximum The points in an interferance pattern where the intensity is brightest Meson A type of hadron made up of a quark and an antiquark Minimum The points in an interference pattern where the intensity is lowest Model A simplified picture of representation of a real physical situation Moment The turning effect of a force around a turning point Monochromatic A light source that is all of the same wavelength Nucleon A particle in the nucleus of an atom Nucleon number The number of nucleons in an atom of an element Nucleus The centre of an atom containing protons and neutrons Neutrino A lepton with almost zero mass and zero charge Neutron A neutral baryon with a relative mass of one Newton's first law of motion The velocity of an object will not change unless a resultant force acts on it Newton's second law of motion The acceleration of an object is proportional to the resultant force acting on it Newton's third law of motion If an object A exerts a force on object B them object B exerts an equal but opposite force on object A Ohm's law Provided the temperature is constant the current through an ohmic conductor is directly proportional to the potential difference across it Ohmic conductor A component that has a fixed resistance for a particular temperature Optical density The propery of a medium that describes how fast light travels through it. Light moves slower through a medium with a higher optical density Optical fibre A thin flexible tube of glass of plastic that can carry light signals using total internal reflection [Show Less]
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AQA GCSE Physics Correctly Answered 100%
P1 ... energy The ability to do work energy store a form of energy kinetic energy energy which a body possesses by virtue of being... [Show More] in motion gravitational potential energy energy an object possesses because of its position in a gravitational field thermal energy the internal energy present in a system due to its temperature elastic potential energy the energy stored in elastic materials as the result of their stretching or compressing emit to give off or send out absorb to take in conservation of energy The principle that energy cannot be created or destroyed closed system A system in which energy, but not matter, is exchanged with its surroundings. pendulum A hanging mass that swings back and forth when pulled to one side and let go. work (joules, J) Force x Distance, the exertion of force overcoming resistance or producing molecular change joules the SI unit of work or energy, equal to the work done by a force of one newton when its point of application moves one metre in the direction of action of the force force (newtons, N) A push or a pull Newtons the SI unit of force. It is equal to the force that would give a mass of one kilogram an acceleration of one metre per second per second kilograms the SI unit of mass, equivalent to the international standard kept at Sèvres near Paris mass (kilograms, kg) the quantity of matter which a body contains weight (newtons, N) the force exerted on the mass of a body by a gravitational field. metres (m) a measure of distance or displacement. time (seconds, s) the indefinite continued progress of existence and events that occur in apparently irreversible succession from the past through the present to the future. unit standards for measurement of physical quantities that need clear definitions to be useful precision refers to the closeness of two or more measurements to each other accuracy the degree of closeness of measurements of a quantity to that quantity's true value. friction the resistance that one surface or object encounters when moving over another. gravitational field strength (g) The force per unit mass experienced by a mass placed in a gravitational field. speed (meters/second, m/s) The distance an object travels per unit of time, Distance / Time spring constant (k) a parameter that is a measure of a spring's resistance to being compressed or stretched useful energy Energy converted by a device into the form(s) the device was designed for. wasted energy Energy converted by a device into the form(s) the device was NOT designed for. dissipate to spread out and become less concentrated efficiency The percentage of the input work that is converted to output work. = useful output energy supplied by device (J) / total input energy of the device (J) x 100 order of magnitude estimate of quantity to the nearest power of ten power (work/time, J/t) the rate of doing work Watts (W) the SI unit of power, equivalent to one joule per second P2 ... thermal conductivity The ability of an object to transfer heat conduction Form of heat transfer where heat energy is directly transferred through direct contact. conductor A material that allows heat and electricity to pass through it. insulator A material that does not allow heat or electrons to move through it easily. infrared radiation Electromagnetic waves with wavelengths that are longer than visible light but shorter than microwaves; heat radiation temperature (Celsius, C) A measure of the average kinetic energy of the particles in a sample of matter Celsius (C) a scale of temperature on which water freezes at 0° and boils at 100° under standard conditions. Kelvin (K) the SI base unit of thermodynamic temperature, equal in magnitude to the degree Celsius, where 0 is defined as absolute zero; [K] = [°C] + 273.15 absolute zero The coldest temperature, 0 Kelvin or -273.15 Celsius, that can be reached. It is the hypothetical temperature at which all molecular motion stops. reflect the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated; bouncing back transmit to send on, pass along, send out black body An ideal absorber of electromagnetic radiation that would absorb all the radiation that was incident upon it. Would also be an ideal emitter, and would emit electromagnetic radiation with a spectrum that depended only on the temperature of the body. black body radiation radiation from a theoretical perfect emitter (and absorber) of radiation at all wavelengths. specific heat capacity (joules, J) the amount of heat energy required to raise the temperature of one gram of substance by one degree celcius convection Process by which, in a fluid being heated, the warmer part of the mass will rise and the cooler portions will sink; the transfer of heat by the movement of a fluid vacuum An empty space where no particles of matter exist P3 ... biofuel fuel created from living matter, such as trees renewable A natural resource that can be replaced at the same rate at which the resource is consumed carbon-neutral A process, or series of processes, in which as much carbon dioxide is absorbed from the air as is given out. nuclear fuel an energy source that results from splitting atoms nucleus The central core of an atom which contains protons and neutrons. electron A subatomic particle that has a negative charge reactor core Term encompassing fuel rods, control rods and absorber rods of a nuclear reactor which together with the moderator substance are in a steel vessel through which coolant is pumped. wind power The use of a windmill to drive an electric generator wave power electrical power produced from ocean waves that are used to turn an electrical generator hydroelectric power Electricity generated by flowing water tidal power Electricity generated by the movement of sea water caused by the tides solar power energy from the sun that is converted into thermal or electrical energy geothermal energy Energy from steam or hot water produced from hot or molten underground rocks. P4 ... proton A subatomic particle that has a positive charge and that is found in the nucleus of an atom neutron A subatomic particle that has no charge and that is found in the nucleus of an atom ion A particle that is electrically charged (positive or negative) electric field a field of force surrounding a charged particle static electricity An accumulation of electric charge on an insulated body. induction The transfer of charge without contact between materials charge (coulomb, Q) A measure of the extra positive or negative particles that an object has. current (amperes, A) the rate of flow of electric charge; current = voltage/resistance; I = V/R; amperes = volts/ohms electrochemical cell a device capable of generating electrical energy from chemical reactions battery consisting of two or more electrochemical cells switch A device for making, breaking, or changing the connections in an electrical circuit. indicator designed to emit light as a signal when current passes through it; ex. a bulb. diode A device that permits current to flow through it in only one direction. LED light-emitting diode; permits current to flow through it in only one direction, emits light when current flows through it ammeter A meter that measures the flow of electrical current in amperes fixed resistor Resistors that have a value that cannot be changed. variable resistor A resistor whose value can be varied between its minimum and maximum values. fuse Electrical device that can interrupt the flow of electrical current when it is overloaded, often by melting heater Converts electrical energy to heat voltmeter A device used to measure voltage, or electrical potential energy difference charge flow Negative to positive terminal; (Q) = current (A) x time (s) coulombs (Q) the SI unit of electric charge, equal to the quantity of electricity conveyed in one second by a current of one ampere. amperes (A) a unit of electric current equal to a flow of one coulomb per second. volts (V) the SI unit of electromotive force, the difference of potential that would carry one ampere of current against one ohm resistance. potential difference voltage; the work done when a coulomb of charge passes between the points; voltage (volts, V) = work done (joules, J) / charge (coulombs, Q) component any basic discrete device or physical entity in an electronic system series circuit A circuit in which all parts are connected end to end to provide a single path of current. parallel circuit A closed electrical circuit in which the current is divided into two or more paths and then returns via a common path to complete the circuit. resistance (ohms, Ω) a material's opposition to the flow of electric current. ohms (Ω) the SI unit of electrical resistance, transmitting a current of one ampere when subjected to a potential difference of one volt. thermistor A resistor that changes its resistance with a change of temperature light-dependant resistor A resistor that changes its resistance with a change of light intensity P5 ... alternating current an electric current that changes direction at regular intervals direct current an electric current that flows in one direction steadily live wire The brown wire in a cable or plug; carries a high voltage around the house neutral wire The blue wire in a cable or plug; carries current away from the component oscilloscope a laboratory instrument that is capable of displaying a graph of voltage as a function of time frequency 1/time taken for 1 cycle earth wire It connects the casing of the electrical appliance to ground via the earth terminal of the plug. Its insulation is coloured green and yellow. In the event of an appliance malfunction resulting in the casing becoming live, it provides a route to ground for the current. This will help prevent electric shock. resistance heating As current flows through a conductor, heat is produced by the resistance of the conductor. P6 ... density Mass / Volume; a measure of how much mass is contained in a given volume. volume A measure of the size of a body or region in three-dimensional space meniscus The curved upper surface of a liquid column that is concave when the containing walls are wetted by the liquid and convex when not. measuring cylinder Used to measure the volume of liquids accurately. gas A state of matter with no definite shape or volume solid A form of matter that has a definite shape and volume liquid A state of matter that has no definite shape but has a definite volume. physical changes Any change that DOES NOT alter the chemical composition of a substance. vaporisation When an substance changes from liquid to gas condensation The change from a gas to a liquid sublimation a change directly from the solid to the gaseous state without becoming liquid freezing The change of state from a liquid to a solid deposition Change from a gas directly to a solid conservation of mass The principal stating that matter is not created or destroyed during a chemical reaction melting point The temperature at which a solid becomes a liquid boiling point The temperature at which a liquid changes to a gas freezing point The temperature at which a liquid changes into a solid latent heat heat absorbed or radiated during a change of phase at a constant temperature and pressure internal energy sum of the kinetic and potential energies of all particles in the system specific latent heat of fusion amount of energy per unit mass required to change phase of a substance from a solid to a liquid at constant temperature and pressure specific latent heat of vaporisation amount of energy per unit mass required to change phase of a substance from a liquid to a gas at constant temperature and pressure gas pressure results from the force exerted by a gas per unit surface area of an object Brownian motion the random movement of particles in a fluid pressure (pascals, Pa) force / area; Force per unit area Boyle's law P1V1 = P2V2; the relationship between the pressure and volume of a gas at constant temperature is inversely proportional; when volume increases, pressure decreases. pascals (Pa) the SI unit of pressure, equal to one newton per square metre P7 ... Geiger counter Radiation detector that produces a click or a flash of light when a charged particle is detected. alpha radiation Radiation that is made up of alpha particles; 2 protons and 2 neutrons. High ionisation, but low penetration. Is easily blocked with paper. beta radiation Consists of electrons, is halted by an aluminum plate that is a few mm thick or a couple of mm of lead gamma radiation High-energy electromagnetic radiation emitted by the nuclei of radioactive atoms. radioactivity the emission of ionising radiation or particles caused by the spontaneous disintegration of atomic nuclei plum pudding model J.J Thomsons model of an atom, in which he thought electrons were randomly distributed within a positively charged cloud photon A particle packet of electromagnetic radiation with no mass that carries a discrete amount of energy atomic number The number of protons in the nucleus of an atom mass number the sum of the number of neutrons and protons in an atomic nucleus isotopes Atoms of the same element that have different numbers of neutrons. alpha particle A cluster of 2 protons and 2 neutrons emitted from a nucleus in one type of radioactivity beta particle a high-speed electron or positron emitted in the decay of a radioactive isotope neutron emission a type of radioactive decay where a neutron is released from the nucleus, decreasing the mass number by one ionisation the process where an atom loses or gains an electron [Show Less]
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AQA A Level Physics Questions and Answers 2022/2023
Longitudinal wave Particle vibration is parallel to direction of wave propagation Examples of a longitudinal wave Sound waves, seismic p-waves ... [Show More] Transverse wave Particle vibration is perpendicular to direction of wave propagation Only transverse waves can be polarised Examples of a transverse wave Electromagnetic radiation, seismic s-waves Particle displacement The distance of a particle from its equilibrium position in given direction Amplitude the maximum displacement of a particle (wave) from its equilibrium (or rest) position Frequency Number of oscillations (of a particle) per second Time period The time for one complete oscillation Wavelength (for non stationary wave) Shortest distance between two points in phase wavelength for stationary wave Distance between alternate nodes or distance from peak to peak/ trough to trough Diffraction Spreading out of a wave (when it passes through a gap or past the edge of an object) Refraction Wave bends/changes direction when its speed changes Polarisation (transverse) wave oscillation is in one plane Application of polarisation in sunglasses • Light reflected from surfaces is (weakly) polarised in one plane (horizontal) • Polaroid in sunglasses can be orientated to remove this reflected light • Reducing glare Application of polarisation in tv transmitters and aerials • Signals from tv transmitter (radio waves) are polarised • Aerials need to be orientated (rotated) so they are in same plane as the transmitted signal • For maximum signal strength Superposition Where two or more waves meet, the resultant displacement equals the vector sum of the individual displacements Conditions for formation of stationary waves • Two waves travelling past each other in opposite directions • With the same wavelength (or frequency) • Similar amplitudes Monochromatic Single wavelength Safety with a laser • Avoid looking along the beam of a laser • Wear laser safety goggles • Avoid reflections • Put up a warning sign that a laser is in use Properties of laser light • Monochromatic - only a single wavelength • Coherent - waves have a constant phase difference • Collimated - produces an approximately parallel beam Sketches of stationary waves for first 4 harmonics Length of string = L 1st Harmonic λ = 2 L 2nd Harmonic λ = L 3rd Harmonic λ = 2/3 L 4th Harmonic λ = ½ L Coefficient of friction µ µ = p A = mass/length = density x Area How does frequency change when very high tension is used on fixed string first harmonic experiment? diameter of string reduces as Tension increases this means there is a lower mass per unit length so frequency is higher than expected Nodes and antinodes Nodes - points of no oscillation / zero amplitude Antinodes - points of maximum amplitude Coherent sources waves (from two sources) that have: • a constant phase difference • same wavelength (or frequency) Appearance of interference fringes from two vertical slit illuminated with yellow light • Vertical or parallel • Equally spaced • Black and yellow bands Fringe width, w, changes Slits closer together w - increases Screen further away w - increases Shorter wavelength (eg blue light) w - decreases Width of slits is reduced (Young's slits) • More interference fringes (more of the pattern) are observed • Fringe spacing remains the same because • Greater amount of diffraction of light through each slit • So bigger region of overlap of the diffracted light from each slit • So more fringes can be observed Explanation of formation of fringes with Young's slits • Interference fringes formed • Where light from two slits overlaps • The light from the two slits is coherent • Bright fringes formed where constructive interference • because light from the two slits is in phase (path difference equals a whole number of wavelengths) • Dark fringes formed where destructive interference • Because light from the two slits is in anti-phase (path difference equals a whole number + 0.5 wavelengths) Appearance of white light through Young's slits • Central fringe would be white • Side fringes are (continuous) spectra • Bright fringe would be blue on the side nearest the central fringe. • Bright fringes merge further away from centre. appearance of diffraction pattern from a single slit • Central bright fringe has twice width of other bright fringes • The other bright fringes have a much lower intensity • and are equally spaced Single slit pattern changes Narrower slit width • Wider pattern / increased separation • Reduced intensity Shorter wavelength • Narrower pattern / reduced separation Lines per mm of a grating Spacing, d, of slits on a diffraction grating given by: d = 1/(number of lines per mm) in mm Derivation of nλ = d sinθ Between slits a and b: Path difference to nth maximum = nλ From trigonometry sin θ = nλ / d Hence nλ = d sinθ NOTE Path difference between light from slits a and c to nth maximum is nλ + nλ = 2nλ Applications of gratings to spectral analysis of light from stars • Dark lines in spectrum from a star (absorption spectrum) • Reveal the composition of (elements present in) the star's atmosphere How does light change moving from air to glass • speed - decreases (slows down) • wavelength - decreases (gets shorter) • frequency - remains constant (stays the same) Conditions for total internal reflection • Angle of incidence is greater than the critical angle • The refractive index of the material light is going from is greater than the refractive index of the material the light is going to. Total internal reflection Where all the light is reflected back into the material Critical angle Angle of incidence which produces an angle of refraction of 90 degrees. Structure of an optical fibre Central core, surrounded by cladding. Refractive index of core must be greater than refractive index of cladding (to ensure total internal reflection) Purpose of cladding • prevents crossover of signal/data to other fibres • prevents scratching of the core • reduces pulse broadening/dispersion Use of optical fibres • Communication - improve transmission of data/high speed internet • Endoscopes - improved medical diagnosis How do pulses of light change travelling down optical fibres • reduced amplitude due to absorption/energy loss and scattering within fibre • pulse broadening due to multipath dispersion from rays taking different paths and different times to travel down same fibre How is multipath dispersion reduced Core of fibre is made very narrow/thin. [Show Less]
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AQA GCSE Physics Questions and Answers 2023
Work Done (J) Force × Distance in direction of force Hooke's Law (force applied to spring) (N) Spring Constant × Extension Pressure (Pa) ... [Show More] Force on object ÷ Area of object Kinetic Energy (J) ½ × Mass × Speed² Gravitational Potential Energy (J) Mass × Gravitational Field Strength × Height 1. Power (W) Energy transferred ÷ Time 2. Power (W) Potential Difference × Current 3. Power (W) Current² × Resistance Resistance (Ω) Potential Difference ÷ Current 1. Efficiency Useful output energy ÷ Total input energy 2. Efficiency Useful power output ÷ Total power input Charge (Coulombs) Current × Time Energy Transferred (J) Charge × Potential Difference Density (Kg/m³ or g/cm³) Mass ÷ Volume [Show Less]
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