Refraction is the change in direction of a wave as it travels from one medium into another.  It explains why a pencil which is partially submerged in a glass of water appears to be broken; it also explains loads of other things, such has how glasses allow us to see objects more clearly, and where rainbows come from.

This video is a short introduction to this important topic, and will give you everything which you need for the final exams.

Key Words

normal, wavelength, wavefront, refraction, light, angle, incidence