Question

A ray of light makes an angle of ${10}^o$ with the horizontal and strikes a plane mirror which is inclined at an angle $\alpha$ to the horizontal. The angle $\alpha$ for which the reflected ray becomes vertical is

• A. $40$
• B. $30$
• C. $60$
• D. $50$

Answer 1

The correct option is D $50$

Angle between incident and reflected ray $={80}^{\circ }$

Angle of incidence $=$ Angle of reflected ray $={40}^{\circ }$

Angle of reflected ray with mirror $=90°-40°=50°$

So angle with horizontal $=90°-50°=40°$