Unit 3 Properties of waves
Refraction of light
- Light rays can change direction when passing from one material into another because the rays move at different speeds in the two materials.
- Notice that the angle of incidence i and the angle of refraction r always lie between the light beam and the normal.
- A material in which light travels slowly is said to be optically dense.
- When travelling from an optically less dense material to a more dense material (such as air to glass), light bends towards the normal (diagram on the left above).
- When travelling from an optically more dense material to a less dense material (such as glass to air), light bends away from the normal (diagram on the right above).
When light enters a different material:
- the frequency stays the same
- the wavelength changes
- the speed changes.
When a light ray travels along the normal from air into glass, it passes straight through (undeviated), but it slows down.