Refraction is the change of direction of a propagating wave or radiation on passing into a medium of different density (e.g. air - glass, glass- air). The degree of deflection depends on the ratio of the refractive indices n(i) of the two media. In general they depend on the wave length of the radiation. The phenomenon of refraction is employed in optical equipment to guide the light rays. In the case of the prism, on the other hand, it can be used to break down the incident light into the colours of the spectrum.
