1. (a) What is meant by critical angle?
(b) The critical angle for a medium is 420.
Find the
refractive index of the medium.
2. Describe the structure of an optical fibre.
Give two advantages of an optical fibre when used in telecommunications.
3. Describe
an experiment to find the refractive index of water.
4. On a hot day the road ahead may appear to be wet. Explain.
5. Show, using a diagram, how a prism may be used to turn a ray of light through 1800.
6. In an experiment to verify Snell’s law, a student
measured the angle of incidence i
and the angle of
refraction r for a ray of light entering a substance. This was
repeated for different values of the angle of incidence. The following data was
recorded.
|
i / degrees |
20 |
30 |
40 |
50 |
60 |
70 |
|
r / degrees |
14 |
19 |
26 |
30 |
36 |
40 |
Describe, with the
aid of a diagram, how the student obtained the angle of refraction. (9)
Draw a suitable graph on graph paper and explain how your graph verifies
Snell’s law. (18)
From your graph, calculate the refractive index of the substance. (9)
The smallest angle of incidence chosen was 20o.
Why would smaller values lead to a less accurate result? (4)