The laws of refraction can be stated as follows:
(a) The incident ray and the refracted ray are on the opposite sides of the normal at the point of incidence and all three lie in the same plane.
(b) For a given pair of media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant.
i.e. sin i / sin r = constant
Where, i = angle of incidence,
r = angle of refraction.