Science Quiz - Light 01 (Answers)
This KS3 Science quiz takes a look at light. Light travels as waves and comes from luminous objects. Most luminous objects are luminous because they are hot. It is possible to have luminous objects that are cold, for example, glowsticks. These rely on chemical reactions and not heat to produce their light. Light can travel through transparent or translucent objects. We can see objects that are not luminous because everything reflects light to a lesser or greater degree. The reflected light rays bounce off objects and into our eyes.
The way that light reflects from objects, including mirrors, is predictable. It can be worked out using ray diagrams. You start by drawing the surface off which the light is reflected. Then you draw in the normal. This is an imaginary line at ninety degrees (a right angle) to the surface. The normal is drawn as a dotted or dashed line to show that it is different to a ray of light. Next you draw the incident ray at the correct angle (measured from the normal and not from the reflecting surface). The reflected ray is then drawn in at the same angle, but on the other side of the normal.
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You can find more about this topic by visiting BBC Bitesize - Light Waves
It changes direction when it meets a surface that reflects it
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Light travels at almost 300,000,000 metres per second in a vacuum
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Light can travel through translucent material
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Translucent means allowing light to pass through but diffusing it so that people and objects on the opposite side are not clearly visible. A frosted window is translucent but not transparent. Tracing paper is another example of a translucent material
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A luminous object gives out light. The Moon reflects light but does not give out light of its own
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If you went deep into a cave, a long way from the entrance and turned off your torch, you would not be able to see your hand if it was right in front of your face because there would not be enough light reflected into your eyes
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Concave and convex mirrors are curved
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In actual fact, the same is true of curved mirrors but it is much more difficult to draw and measure
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Rough surfaces give diffuse reflection
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It is also drawn touching the surface at the same point as the ray of light
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