Write laws of refraction. Explain the same with the help of ray diagram, when a ray of light passes through a rectangular glass slab.

The laws of refraction are:

(a) The two laws of refraction of light are as follows:

1. The incident ray, the refracted ray and the normal at the point of coincidence, lie in the same plane.

2. The second law of refraction is also known as Snell’s law of refraction and it states that: the ratio of Sine of the angle of incidence to the sine of refraction is constant for a given pair of media. It establishes a relation between angle of incidence and angle of refraction.

It can be expressed mathematically as follows:

It can be shown with the following diagram:

Here, EO is the incident ray, OO’ is the refracted ray and O’H is the emergent ray.

Since the incident ray, refracted ray and the emergent ray are in the same plane which is the first law of refraction. Moreover as light ray enter from a rarer to a denser medium, it bends towards the normal and when it comes out from glass to air, it bends away from the normal. The refractive index can be calculated by taking the ratio of sine of the angle of incidence to the ratio of sine of refraction which is also the Snell’s law.