State the laws of refraction.

(i) The incident ray, the refracted ray and the normal to the interface of two transparent media at the point of incidence, all lie in the same plane.

(ii) The ratio of sine of angle of incidence to the sine of angle of refraction is a constant, for the light of a given colour and for the given pair of media. This law is also known as Snell’s law of refraction.

If $i$ is the angle of incidence and $r$ is the angle of refraction, then,

${}^1{\mu }_2=\frac{sini}{sinr}$

This constant value is called the refractive index of the second medium

with respect to the first.