What is reflection?
When light or other wave rebounds at a boundary between two materials
What is a virtual image?
The rays do not actually come
... [Show More] from a virtual image. They just appear to come from it. A virtual image cannot be formed on a screen.
What is refraction?
When a wave passes from one material to another its speed may change. This may cause a change in direction.
What is diffraction?
The spreading out of waves when they pass through a gap or go round the edge of an obstacle
How can you increase the amount of diffraction when a wave passes through a gap?
Decrease the gap size or increase the wavelength. Maximum diffraction occurs when the wavelength of the wave is about the same as the gap size.
Give two properties that all parts of the electromagnetic spectrum have in common.
They are all transverse and they all travel at the speed of light through a vacuum.
What is a wave?
Waves transfer energy and information without transferring matter.
What is a transverse wave?
A wave where the oscillations are perpendicular to the direction of energy transfer.
What is a longitudinal wave?
A wave where the oscillations are parallel to the direction of energy transfer.
What is the law of reflection?
The angle of incidence is equal to the angle of reflection.
What do we call a reflected sound wave?
An echo.
What is the critical angle?
The angle of incidence at which the angle of refraction is 90 degrees.
Give three uses of total internal reflection
Optical fibres, cat's eyes and submarine periscopes.
State some uses for optical fibres.
Communication, endoscopes, decorative lights.
State two conditions required for total internal reflection to take place.
The light must be moving from a more optically dense material to a less optically dense material and the angle of incidence must be greater than the critical angle.
What is the wavelength of a wave?
The distance between two identical points on the wave e.g. crest to crest.
What is the amplitude of a wave?
The maximum displacement from the equilibrium position.
What is the frequency of a wave?
The number of complete cycles or waves per second.
What is the time period of a wave?
The time for one complete wave to pass.
What is ultrasound?
Sound wavs of frequency grater than 20,000Hz.
Give an example of a transverse wave.
Any member of the electromagnetic spectrum e.g. UV, radio, IR, microwaves OR water waves.
Give an example of a longitudinal wave.
Sound or ultrasound.
Describe how sound waves move through the air.
Longitudinal vibration of air molecules. The directions of vibration and energy transfer are parallel. The wave passes as a series of compressions and rarefactions.
State two changes which would increase the amount of diffraction when a wave passes through a gap.
Increasing the wavelength and decreasing the size of the gap.
What is an analogue signal?
A continuously varying signal which can have any values in a range.
What is a digital signal?
A signal which only has two values (on and off).
State one advantage of using digital signals rather than analogue signals.
Digital signals can carry more information in the same amount of time, are less prone to interference and can be restored.
Give one example from everyday life of the use of a digital signal.
Telecommunications/CDs.
Suggest a way that digital signals can be made to carry more information.
Multiplexing. This is where multiple signals are sent down a cable at the same time.
Give a use of radio waves.
Broadcasting and communications.
Give a use of microwaves.
Cooking and satellite transmissions.
Give a use of infrared.
Heaters and night vision equipment.
Give a use of visible light.
Optical fibres and photography. [Show Less]