Question

A mirror is inclined at an angle of $\theta$ with the horizontal. Let a ray of light be incident at an angle $\theta$ as shown, then what is the angle made by the reflected ray with the horizontal ?

• A. $\theta$
• B. $2\theta$
• C. $\frac{\theta }{2}$
• D. zero

Answer 1

Answer: (D)

For reflection, angle of incidence $i$ = $r$ angle of reflection
$\therefore$ The refelceted ray makes the same angle $\theta$ with the mirror as like the incident ray at the point of incidence on the inclined mirror.
Draw a normal to the inclined mirror, then then incident ray is at an angle $\theta$ with the mirror and at $90^0-\theta$ with the normal.
Hence, according to the law of reflection, the reflected ray will be at $90^0-\theta$ with the normal and $\theta$ with the inclined mirror.
Thereby, the reflected ray becomes parallel to the horizontal.