Question

A ray of light when incident upon a prism suffers a minimum deviation of ${39}^{\circ }.$ If the shaded half portion of the prism is removed, then the same ray will be-

• A. Suffer a deviation of ${19.5}^{\circ }$
• B. Suffer a deviation of ${78}^{\circ }$
• C. Not suffer any deviation
• D. Will be totally internally reflected

Answer 1

The correct option is A Suffer a deviation of ${19.5}^{\circ }$

The minimum deviation suffered by a prism is,

$\delta =(\mu -1)A$

$\delta \propto A$

$\Rightarrow \frac{{\delta }_2}{{\delta }_1}=\frac{A_2}{A_1}$

$\Rightarrow \frac{{\delta }_2}{{\delta }_1}=\frac{\frac{A}{2}}{A}=\frac{1}{2}$

$\therefore {\delta }_2=\frac{{\delta }_1}{2}$

$\Rightarrow {\delta }_2=\frac{39}{2}={19.5}^{\circ }$

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(A\right)$ is the correct answer.