9
Answers
Year 9 Science
1. SIMPLE REFRACTION
The pencil appears larger.
The printed page appears closer.
a) Rest a pencil in a beaker nearly full of water. What do you see.
b) Look at print thought the prism. What do you see.
2. RECTANGULAR PRISM
a) What happens to the direction of the ray of light as it enters the perspex?
The direction of the ray of light changes. It is bent or refracted towards
the normal.
b) When light passes from air into perspex, in what direction is it refracted?
The ray is refracted towards the normal.
c) Does all the incident light enter the perspex? Explain.
No. Some of the light is reflected, refracted and absorbed.
d) Does all of the light which reaches the opposite side of the block, pass out into the air? Explain.
Similarly to light entering, light leaving the perspex will also be reflected,
refracted and absorbed.
e) For what angle of incidence is there no change in direction when light passes from air into perspex?
When the incident ray is 90° to the perspex.
f) How does the angle of refraction vary as the angle of incidence is changed gradually?
As the angle of incidence is increased, the angle of refraction increases.
g) How does the angle of the emergent ray compare with the direction of the incident ray?
Both rays are parallel and have the same angle with the perspex.
EXERCISES
1. Some window glass has a crinkled or rough surface. Explain what main effect this has on light.
The glass has a rough surface which causes the light rays to be refracted in
many different directions. Diffuse refraction occurs, scattering the light.
2. Why does a pool of clear water look shallower than it really is? Use a diagram in your answer.
Light travels in straight lines and is refracted when it passes through
different mediums.
3. Why do stars twinkle?
Stars give off their own light via nuclear fusion (ie the sun). This light travels
through space to earth and passes through different densities of gas in our
atmosphere. This refracts and reflects the light rays continuously so the stars
appear to twinkle.
4. Make a list of any other refraction effects that you see around you in everday life.
eg. Fishing line, glasses, contact lenses, looking through windows,
magnifying glass etc.
09 Refraction of Light Ans Page 1 of 1