The Laws of Refraction
1.Incident ray, reflected ray, refracted ray and the normal of the system lie in the same plane.
2.Incident ray, coming from one medium to the boundary of another medium, is refracted with a rule derived from a physicist Willebrord Snellius. He found that there is a constant relation between the angle of incident ray and angle of refracted ray. This constant is the refractive index of second medium relative to the first medium