Question

A ray of light is incident normally on one face of an equilateral prism of refractive index $1.5$.
The angle of deviation is:

• A. ${30}^o$
• B. ${45}^o$
• C. ${60}^o$
• D. ${75}^o$

Answer 1

Answer: (C)

${60}^o$

${\mu }_1\sin i_1={\mu }_2\sin {\gamma }_2$ at surface $BC$

$\begin{array}{c}1.5\sin 60=\left(1\right)\sin \gamma \\ \frac{3}{2}\left(\frac{\sqrt{3}}{2}\right)>1\end{array}$

So TIR Occurs

so Diviation occured only at $6c$

Diviation in afflection $=180-i=180-60$

$={60}^{\circ }$

So option $c$ is correct