Refraction

When light passes from air into a denser material such as glass, water or plastic it slows down. If it meets the join between the materials at an angle then it bends – this is called refraction.

When light travels from air into a denser material such as water or glass it slows down and bends towards the normal. When light travels into air from a denser material such as water or glass it speeds up and bends away from the normal.