P&W : Refraction

Question 1

Refraction

Answer 1

The change in speed of light as it passes from one medium to another (e.g. from air to glass)

Question 2

Absolute refractive index

Answer 2

A number greater than or equal to 1 which indiactes the materials ability to refract light.

It is also the ratio of the speed of light in a vacum and the speed of light in the medium

Question 3

Crtical angle

Answer 3

The angle of incidence which produces an angle of refractrion of 90 degrees

Question 4

Total Internal Reflection

Answer 4

Occurs at angle of incidence above the critical angle, when all the light is refracted inside a denser medium. No light escapes.

Question 5

Experiment to determine the refractive index of a medium

Answer 5

What you will need :
Semicircular Perspex Block
Normal Line 
Raybox and incident ray
Refracted ray and pencil crosses.

1. Draw around the semi-circular block and draw in the dashed normal line at 90 degrees to the midpoint of the straight edge
2. Set up the ray box with an incident ray of 10 degrees to the normal line and mark in the refracted ray with two pencil crosses as shown
3. Remove the ray box and the semicircular block then measure the angle of incidence and the angle of refractrion from the normal using a protactor
4. Repeat for anlge of incidneces from 20 degrees to 80 degrees.
5. Plot the graph of sin of the angle of incidence (y-axis) against sine of angle of refraction
6. The gradient of the graph is the is the refractive index of the material of the semicircular block.