Refraction of light is the bending of light as it passes from one medium to another, such as from air to water or from glass to air. This phenomenon occurs because the speed of light changes as it passes from one medium to another. The change in speed causes the light to bend, or refract. It is responsible for many of the optical phenomena we observe such as rainbows, mirages, and the apparent bending of a stick half-submerged in water.
