Question
A rectangular block is composed of three different glass prisms (with refractive indices $\mu_1, \mu_2$ and $\mu_3$ ) as shown in the figure below. A ray of light incident normal to the lef $t$ face emerges normal to the right face. Then, the refractive indices are related by

Answer

(c)

Ray diagram of ray through the composition of prisms will be

By Snell's law on surface $A B$ and $A C$, we have

$\mu_1 \sin 45^{\circ}=\mu_2 \sin \theta \quad \dots(i)$

and $\mu_3 \sin 45^{\circ}=\mu_2 \cos \theta \quad \dots(ii)$

As $\alpha-\theta=45^{\circ}$, from figure

Squaring and adding Eqs $(i)$ and $(ii)$, we get $\quad \frac{\mu_1^2}{2}+\frac{\mu_3^2}{2}=\mu_2^2$

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