Optics 1 Question 5
5. A ray of light travelling in the direction $\frac{1}{2}(\hat{\mathbf{i}}+\sqrt{3} \hat{\mathbf{j}})$ is incident on a plane mirror. After reflection, it travels along the direction $\frac{1}{2}(\hat{\mathbf{i}}-\sqrt{3} \hat{\mathbf{j}})$. The angle of incidence is
(a) $30^{\circ}$
(b) $45^{\circ}$
(c) $60^{\circ}$
(d) $75^{\circ}$
(2013 Adv.)
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Answer:
Correct Answer: 5. (a)
Solution:
$$ \tan i=\frac{1 / 2}{\sqrt{3} / 2}=\frac{1}{\sqrt{3}} $$
$\Rightarrow$
$$ i=30^{\circ} $$
