##### DEFINITION

The law of refraction states that for a ray that is incident (i.e. acting on) on the surface between two media, the ratio of the sine of the angle of the incident ray to the sine of the angle of the refracted ray is equal to the ratio of the ray’s velocity in the first medium to the ray’s velocity in the second medium. This is given that the incident ray, the refracted ray, and the normal to the surface, all lie in the same plane**[1]****[2]**.