Question

A ray of light makes normal incidence on the diagonal face of a right angled prism as shown in figure. If $\theta ={37}^o$, then the angle of deviation after second step (from AB) is (sin ${37}^o=3/5$ )

• A. ${53}^o$
• B. ${74}^o$
• C. ${106}^o$
• D. ${90}^o$

Answer 1

The correct option is A ${53}^o$

When light strike face $AB$ $\Rightarrow {\sin }_{ic}=\frac{1}{\mu }(\therefore i_c=$ critical angle $)$

$\Rightarrow {\sin }_{ic}=\frac{3}{5}$

$\Rightarrow i_c={37}^{\circ }$

But in face incidance angle $={53}^{\circ }$

$\therefore$ reflection takes place

$\angle i⟩<\angle i_c$

9n face BC Incidence angle $={37}^{\circ }$

$\begin{array}{c}i=ic\\ \therefore \angle \gamma =90\end{array}$

$cD$ is divergent ray angle blw incident and divergent ray is ${53}^{\circ }$ (from figure)

Hence (A) is correct