1. Refraction

2. Refraction : Bending light
 The speed of light waves depends on the material they are travelling through.
 If the light waves enter a different material [e.g. from glass into air] the speed changes.
 This causes the light to bend [or refract].
Air = Fastest
Glass = slower
Diamond = slowest
Glass

3. Refraction - at the air-glass boundary

4. Refraction : Investigating Refraction
1. Place a rectangular glass block on a sheet of paper and draw around it.
Angle i
2. Draw a normal line [90º] along the top surface of the block.
Angle r
Shine rays of light with incident [i] angles of 30º, 60º and 0º into the block, making sure they all hit where the normal line crosses the glass surface].
Measure angle “r” each time and record your answers .

5. Refraction : What happened?
 Put your answers into the table below:
 Write 2 ‘rules’ to describe:
a) what happens to the ray as it enters the glass.
b) what happens to the ray as it re-enters the air.

6. Air to Glass: angle of incidence > angle of refraction I > r
As the light ray moved from air into glass it moved towards the normal.
If light rays move from a less dense medium (air) to a more dense medium (glass) they ‘bend’ towards the normal.

7. Glass to Air angle of incidence < angle of refraction i < r
As the light ray moved from glass into air it moved away from the normal.
If light rays move from a more dense medium (glass) to a less dense medium (air) they ‘bend’ away from the normal.
If the surface the light ray is incident upon is parallel to the surface it emerges from than the emergent ray makes the same angle with the normal as the incident ray.
(If the two surfaces of the block are parallel, then the ray at the start is parallel to the ray at the end).

8. Angle of incidence = 0°
When the angle of incidence is 0 the light ray is not deviated from its path.
Un-deviated light ray

9. Refraction in a rectangular block

10. angle of emergence - definition
angle of emergence - definition. ... The light refracts or bends as it enters the glass, then carries on and emerges at a new angle back into the air. The ray of light coming out is parallel to the incident ray and the angle of emergence is the same as the angle of incidence.