State the laws of refraction of light.

Laws of refraction of light: 

1. The incident ray, the refracted ray and normal to the surface of separation at the point of incidence, all the three, lie in the same plane. 

2. For a given pair of media, the ratio of the sine of the angle of incidence and the sine of the angle of refraction is constant.

Mathematically, 

                    $\frac{\sin \mathrm{i}}{\sin \mathrm{r}} = {\mathrm{n}}_{21} (\mathrm{a} \mathrm{constant}).$ 

The ratio n₂₁ is called refractive index of the second medium with respect to the first medium.
The second law of refraction is also called Snell’s law of refraction.