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Mirrors reflect light.

# Waves - Reflection and Refraction

This GCSE Physics quiz about waves looks at reflection and refraction. Reflection occurs when any wave reaches a boundary between two different media. The amount of reflection depends on the nature of the medium that the wave is hitting. At GCSE, you will have studied this only for light waves, but what you have learnt about light reflection is equally applicable to any wave. All waves follow the laws of reflection, so make sure you revise them well. In the exam, stay calm if you come across a question that asks you about the reflection of water waves, earthquake waves, radio waves or sound waves. Simply pretend they are light waves and that should help you find the answer.

OK, lets think about light waves now. When light hits an opaque surface, some of the energy it carries is reflected and some is absorbed.

1.
A light ray is reflected off the surface of a plane mirror at 40o to the normal. What is the angle of reflection of the reflected ray?
30o
40o
50o
60o
The angle of reflection is always equal to the angle of incidence. This is known as Snell's Law or the law of reflection
2.
What determines how fast light travels in a medium?
Size of the medium
Shape of the medium
Refractive index of the medium
Colour of the medium
The higher the refractive index, the slower the wave travels and the more it will bend on entering the medium
3.
What equation can be used to calculate the refractive index of a substance?
Refractive index = 1 x sin c
Refractive index = 1 / sin c
Refractive index = 1 – sin c
Refractive index = 2 / sin c
Using two different types of glass that have different refractive indices to make compound lenses for optical instruments avoids the defect of chromatic aberration
4.
The critical angle of diamond is 24 degrees. What is its refractive index?
0.6
4.9
2.4
0.4
Diamond has a small critical angle which means a lot of light is totally internally reflected - this is why diamonds are so sparkly
5.
Another equation for calculating the refractive index of a substance is ...
Refractive index = sin i x sin r
Refractive index = sin r / sin i
Refractive index = sin c / sin r
Refractive index = sin i / sin r
Whichever way that you work it out, the refractive index has no units
6.
If light enters a medium with an angle of incidence of 23 degrees and has an angle of refraction of 18 degrees, what is the refractive index of the medium?
0.12
1.3
0.8
0.7
Simple substitution into the equation
7.
If a shiny surface is not smooth, what will happen to light rays incident upon it?
They will be reflected in numerous directions
They will be reflected towards one point
They will pass straight through the material
The light will be absorbed by the material
Each tiny section of the surface still follows Snell's law
8.
When a light ray travels from air into glass, what can you say about the size of the angle of refraction compared to the angle of incidence?
It is bigger
It is the same
It is smaller
It is zero
Glass is a more dense medium than air therefore the light refracts towards the normal
9.
What direction does the incident ray bend when travelling from glass to air?
Towards the normal
Towards the glass
Towards the sea
Away from the normal
This is exactly the opposite to the case in the previous question because the light is travelling from a more dense medium into a less dense medium
10.
Which of the following can reflect light?
Mirror
Water
Glass
All of the above
Light can be reflected by most surfaces. The above are examples of a few which can be regularly observed in our daily lives. It does not just have to be a mirror which reflects light
You can find more about this topic by visiting BBC Bitesize - Reflection and refraction of waves

Author:  Martin Moore