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25 Cards in this Set

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What are natural sources of light?
Natural sources of light are materials or objects that emit their own light, i.e. they are luminous. E.g. sun, candle, fires, lightning etc.
What are luminous objects?
Objects that emit their own light.
Light is a form of _____ in the form of _____ waves.
energy, electromagnetic
What are artificial sources of light?
Artificial sources of light are materials or objects that are manufactured to emit light. E.g. torches, lasers, TV screens.
Light energy travels by means of _____ _____.
electromagnetic waves
Electromagnetic waves do not require a ______ through which to travel.
material, or medium
What is a light ray?
A light ray is a line indicating the direction in which light waves are travelling.
What conditions must exist for the human eye to see an object?
Light from the object must enter the eye.
How can we see non-luminous objects?
Non-luminous objects may be seen only by the light they reflect.
Define ‘medium’.
A medium is the material substance through which light waves travel.
Define ‘frequency’.
The frequency of a wave is the number of waves which pass any given point in the medium each second, measured in Hertz (Hz) or cycles per second (cps).
Define ‘period’.
The period of a wave is the time taken for one complete wave to pass a given point, measured in seconds (s).
Define ‘wavelength’.
The wavelength of a wave is the length of one wave, i.e. the distance between two consecutive wave crests, measured in metres (m).
What is the relationship between frequency and wavelength?
Inverse relationship i.e. frequency = 1/wavelength
Write down the formula for the speed of a wave.
where T = 1/f
The colour of light is determined by the _____ of the light waves.
frequency
Under what conditions does regular reflection occur?
Regular reflection occurs when parallel rays striking a smooth or polished surface are reflected uniformly, i.e. parallel.
State the Laws of Reflection.
1. The angle of incidence is equal to the angle of reflection. 2. The incident ray, reflected ray and the normal are all in the same plane. 3. The incident ray and reflected ray are on opposite sides of the normal.
The angle of _____ is equal to the angle of _____.
incidence, reflection
The _____ ray, _____ ray and the _____ are all in the same plane.
incident, reflected, normal
The incident ray and reflected ray are on _____ sides of the normal.
opposite
Under what conditions does irregular reflection occur?
Irregular reflection occurs when light strikes an irregular, or rough, surface, and light is reflected in many directions.
Define ‘transparent’.
A material is said to be transparent if it allows light to pass through it without interference. E.g. glass.
Define ‘translucent’.
A material is said to be tranlucent if it allows light to pass through it but scatters the light rays, making vision difficult. E.g. frosted glass, tissue paper.
Define ‘lateral inversion’.
Lateral inversion is the left to right reversal of an image, e.g. produced by plane mirrors.