Light Refraction

A straight stick appears bent when partially immersed in water; the sun appears oval rather than round when it is about to set; a stream may appear to be much shallower than you know it to be; the pavement shimmers on a hot summer's day. These are some of the effects caused by the refraction of light as it passes from one medium to another.

As light passes from one transparent medium to another, it changes speed, and bends. How much this happens depends on the refractive index of the mediums and the angle between the light ray and the line perpendicular to their surface, called the normal. Each medium has a different refractive index.

The angle between the light ray and the normal as it leaves a medium is called the angle of incidence. The angle between the light ray and the normal as it enters a medium is called the angle of refraction.