Question

A ray of light travelling in the direction $\frac{1}{2}(i+\sqrt{3}j)$ is incident on a plane mirror in the x-z plane. After reflection, it travels along the direction $\frac{1}{2}(i-\sqrt{3}j)$. The angle of incidence is:

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

The following is the reflection diagram.

$r_1=\frac{1}{2}(\overrightarrow{i}+\sqrt{3}\overrightarrow{j})$

$tan\theta =\frac{\frac{\sqrt{3}}{2}}{\frac{1}{2}}=\sqrt{3}$

$\theta ={60}^{\circ }$

i = ${30}^{\circ }$