Refraction's the change in direction of a wave due to a change in its speed. This's most commonly observed when a wave passes from one medium to another. Refraction of light's the most commonly observed example, but any type of wave can refract when it interacts with a medium, for example when sound waves pass from one medium into another or when water waves move into water of a different depth. Refraction's described by Snell's law, which states that the angle of incidence's related to the ang… (More on Refraction)