State the laws of refraction.

(N/A) $(i)$ The incident ray, the refracted ray, and the normal at the point of incidence all lie in the same plane.
$(ii)$ The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a given pair of media. This law is also known as Snell's law. Mathematically, $\frac{\sin i}{\sin r} = \text{constant} = {_1n}_2$.