Question

A mirror is inclined at an angle $\theta$ with the horizontal. If a ray of light is incident at an angle $\theta$ with the surface of the mirror, then the reflected ray makes the following angle with the horizontal.

• A. $\theta$
• B. $2\theta$
• C. $\theta /2$
• D. Zero

Answer 1

The correct option is D Zero

Let us draw the ray diagram
Let $AO$ be the incident ray and $OB$ be the reflected ray.
Since angle of incidence $\angle AON=90-\theta$
Angle of reflection $\angle NOB=90-\theta$
Also
$\angle MOQ+\angle AOM+\angle NOA+\angle NOP={180}^{\circ }$
$\theta +\theta +90-\theta +\angle NOP={180}^{\circ }$
$\angle NOP=90-\theta$
Which is possible only when $\angle BOP=0$

Why this question? Caution: Laws of reflection are valid for any type of reflecting surface.