Question

Find the angle of deviation in the given figure.

• A. ${15}^{\circ }$ anticlockwise
• B. ${15}^{\circ }$ clockwise
• C. ${30}^{\circ }$ clockwise
• D. ${37}^{\circ }$ clockwise

Answer 1

The correct option is B ${15}^{\circ }$ clockwise

Applying Snell's law at the interface:

${\mu }_1\sin i={\mu }_2\sin r$

$\Rightarrow \sqrt{2}\times \sin 30{}^{\circ }=1\times \sin r$

$\Rightarrow \frac{1}{\sqrt{2}}=\sin r$

$\Rightarrow r=45{}^{\circ }$

Deviation $\left(\delta \right)=(r-i)=({45}^{\circ }-{30}^{\circ })$

$\Rightarrow \delta ={15}^{\circ }$ clockwise

Hence, option $\left(b\right)$ is correct.

Note :- We need to check the condition for $\text{TIR}$, if the rays are travelling from denser medium to rarer medium.