What is refraction?
Refraction is the bending of light when it passes from one transparent material to another, for example from air into water or glass. The bending happens because light changes speed when it moves between materials of different density.
Key idea
Going from a less dense to a denser material (air → water), light slows down and bends towards the normal. Going from denser to less dense (water → air), it speeds up and bends away from the normal.
Everyday examples
Refraction makes a straw in a glass of water look bent at the surface. A swimming pool looks shallower than it really is. A coin at the bottom of a cup can seem to rise when water is poured in. These happen because light from the object bends as it leaves the water and enters the air before reaching our eyes.
Example
A pencil placed in a glass of water appears broken at the water line, but it is still straight — the light has been refracted.
Uses of refraction
Refraction is used in lenses for spectacles, magnifying glasses, cameras and microscopes. Lenses bend light to form images and to help people with poor eyesight see clearly.
Remember
- Refraction is caused by a change in the speed of light.
- Air to water: bends towards the normal.
- Lenses work by refracting light.