Refraction

thumb|A ray of light being refracted in a plastic block In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomenon, but other waves such as sound waves and water waves also experience refraction. How much a wave is refracted is determined by the change in wave speed and the initial direction of wave propagation relative to the direction of change in speed.

ratio of the speed of light in vacuum to that in the medium

cause of vision problems

medical specialty

special kinds of glass used for making various components of optical devices and systems