Refraction is the change in direction that occurs when a wave of light passes from one medium to another, such as from air to glass or from water to air. It occurs because the speed of light is different in different media.
When a light wave strikes an interface between two different media, it is partially reflected back into the first medium and partially transmitted into the second medium. The angle at which the light wave is transmitted is determined by the difference in the refractive indices of the two media.
The refractive index of a material is a measure of the amount of bending that occurs when light passes into that material. The higher the refractive index, the more the light is bent.
