Question

in the figure the path of a parallel beam of a light passing through a convex lens of refractive index n2 kept in a medium of refractive index n1 how are N1 and N2 related to each other​

Answer 1

Given:

The path of a parallel beam of a light passing through a convex lens of refractive index n2 kept in a medium of refractive index n1 has been shown in the attached diagram.

To find:

Relation between n1 and n2.

Solution:

In the 1st case:

The parallel beam of light after getting refracted from the lens converges to meet at a point on the principal axis.

So, the refractive index of the lens is greater than that of the medium such that the rays are deviated towards the normal.

Here the lens acts as a converging lens.

Hence n2 > n1.

In the 2nd case:

The parallel beam of light after getting reflected from the lens divergence away from the principal axis.

This means that refracted Ray moves away from the normal.

Hence the lens acts as a diverging lens.

Hence n2 < n1.