Question

A rays of light passes through four transparent media with refractive indices ${\mu }_1,{\mu }_2,{\mu }_{3}and{\mu }_4$ as shown in the Figure 28.79. The surface of all media are parallel. if the 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 ${\mu }_4={\mu }_1$

for any number of mediums , if ${\alpha }_1$ is angle of incidence at $1^{st}$ interface and ${\alpha }_n$ is angle of refraction at some $n^{th}$ interface then ,

$\frac{{\mu }_1}{{\mu }_n}=\frac{sin{\alpha }_n}{sin{\alpha }_1}$

here the two rays are parallel hence the refractive index of both the medium are same . hence option $D$ is correct