1. 10.3a Bending light
When a ray of light enters a glass block at an angle to the normal, the angle is called its angle of incidence (i).

2. 10.3a Bending light
When the light ray changes direction inside a glass block, its angle to the normal is called its angle of refraction (r). It is smaller than the angle of incidence.

3. 10.3a Bending light
When the light ray leaves a glass block and enters the air, which is less dense, its angle to the normal changes again and becomes bigger.

4. 10.3a Bending light
If you increase the angle of incidence the angle of refraction also increases.

5. 10.3a Bending light Waves Light is a wave.
In diagrams we can represent this more simply as:

6. 10.3a Bending light
Light changes direction when it enters a denser substance at an angle because the part of the wave which hits it first slows down and changes the angle of the whole wave.

7. 10.3a Bending light
Light changes direction when it enters a less dense substance at an angle because the part of the wave which hits it first speeds up and changes the angle of the whole wave.

8. 10.3a Bending light
When light enters a denser substance at right angles all the wave is slowed down at the same time so it does not change direction.