What is meant by 'refraction of light'? Draw a labelled ray diagram to show the refraction of light.

Refraction of light:

The change in direction of light when it passes from one medium to another obliquely is called refraction of light.

Here, the light ray changes its direction or refracts at point $O$ when it travels from air to glass. The ray changes its direction again at point $Q$ when it travels from glass to air.