Question

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

Answer 1

Law of refraction:

1. The incident ray, the refracted ray, and the normal to interface of two transparent media at the point of incidence, all lie on the same plane.
2. Snell's Law; the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant.

i.e.

$\frac{\sin i}{\sin r}=cons\tan t$

$i$ is the incident angle.

$r$ is the refracted angle.

This constant value is called the refractive index of the second medium with respect to the first medium.

Refraction in Glass Slab:

1. In the below glass slab,
   
2. ABCD is a glass slab and EF is an incident ray that strikes the air-glass interface
3. It is observed that incident ray, refracted ray, and normal lie in the same plane: which is in accordance with the first law of refraction.
4. It is also observed that EF is parallel to GH; which means the emergent ray is parallel to the incident ray. This happens because the angle at opposite surfaces of the glass slab is the same.