The phenomenon of bending of light rays as they pass from one medium to another is called refraction of light. The bending of light rays is due to the fact that the speed of light changes as it passes from one medium to another. If the light goes from rarer medium to denser medium, it bends towards the normal and if it goes from denser to rarer medium, it bends away from the normal. The refraction of light obey two laws (a) the incident ray, r refracted ray and the normal at the point of incidence all lie on the same plane and (b). The ratio of sine of angle of incidence and sine of angle of refraction is constant for a given pair of media.
