Question

The angle of the prism is ${30}^{\circ }$. The rays incident at ${60}^{\circ }$ on one refracting surface suffers a total deviation of ${30}^{\circ }$. Find the angle of emergence.

• A. $0^{\circ }$
• B. ${30}^{\circ }$
• C. ${60}^{\circ }$
• D. ${90}^{\circ }$

Answer 1

The correct option is A $0^{\circ }$

Given :
Angle of prism :
$\text{A}={30}^{\circ }$
Deviation of light :
$\delta ={30}^{\circ }$
Angle of incidence at first refracting face :
$i={60}^{\circ }$

We know that, the angle of deviation is given by :
$\delta =(i+e)-A$
$\Rightarrow {30}^{\circ }=({60}^{\circ }+e)-{30}^{\circ }$
$\Rightarrow e=0^{\circ }$

Hence, $\left(a\right)$ is the correct answer.