What do you meanby laws of refraction?

Explanation

Laws of refraction: (i) The incident ray the refracted ray and the normal lie in the same plane (ii) The ratio of sine of angle of incidence (sin i) to the sine of angle of refraction (sin r) for a given pair of media remains constant.
This constnat is called refractive index `(mu)` of the medium in which light enters w.r.t the medium from which light comes i.e. `(sini)/(sinr)=""^(a)mu_(b)`