Question

A ray of light passes through four transparent media with refractive indices${\mu }_1,{\mu }_2,{\mu }_3$ and ${\mu }_4$ as shown in the figure. The surfaces of all media are parallel. If the emergent ray CD is parallel to the incident ray AB, we must have:

• A. ${\mu }_1={\mu }_2$
• B. ${\mu }_2={\mu }_3$
• C. ${\mu }_3={\mu }_4$
• D. ${\mu }_4={\mu }_1$

Answer 1

The correct option is D ${\mu }_4={\mu }_1$

We know that $\mu \sin \theta =constant$

where $\mu =$ refractive index of medium

and $\theta =$ angle between direction of propagation and normal

Here, for medium -1 and medium-4:-

rays are parallel , and hence $\theta$ will be same.

$⟹{\mu }_1={\mu }_4$

Answer-(D)