Question

Figure shows graph of angle of deviation v/s angle of incidence for a light ray. Incident ray goes from medium $1\left({\mu }_1\right)$ to medium $2\left({\mu }_2\right)$. Mark the correct option $\left(s\right)$.

• A. $\frac{{\mu }_1}{{\mu }_2}=\frac{1}{2}$
• B. Critical angle is ${30}^o$
• C. ${\mu }_1>{\mu }_2$
• D. Maximum deviation is ${120}^o$

Answer 1

Answer: (B)

Critical angle is ${30}^o$

At $i={30}^{\circ }$ is critical angle.

ray goes from medium I ( ${\mu }_1$ ) to

medium $2\left({\mu }_2\right)$

For the critical angle and $T1R$

to be happened ${\mu }_1>{\mu }_2$

Sine rule

$\begin{array}{c}{\mu }_1\sin i_1={\mu }_2\sin i_2\\ {\mu }_1\sin 30={\mu }_2\sin 90\\ \frac{{\mu }_1}{{\mu }_2}=2\end{array}$

maximum deviation $=180-i_c=180-30={150}^{\circ }$

so option $B$ is correct