Question

What would be the angle of incidence, if the reflected ray makes an angle of ${120}^{\circ }$ with incident ray?

• A. ${120}^{\circ }$
• B. ${20}^{\circ }$
• C. ${60}^{\circ }$
• D. ${80}^{\circ }$

Answer 1

The correct option is C ${60}^{\circ }$

Let the angle of incidence and angle of reflection be $i$ and $r$ respectively.
According to laws of reflection:
$\angle i=\angle r$
Given :
Reflected ray makes an angle of ${120}^{\circ }$ with incident ray
$\therefore \angle i+\angle r={120}^{\circ }$
$\Rightarrow 2\angle i={120}^{\circ }$ $\Rightarrow \angle i={60}^{\circ }$