Question

Two plane mirrors are inclined to each other ray of light incident on one face at $30{}^\circ$ after reflection from the second retraces the path. What is the angle between the mirrors?

• A. $40{}^\circ$
• B. $60{}^\circ$
• C. $20{}^\circ$
• D. $30{}^\circ$

Answer 1

Answer: (D)

$30{}^\circ$

Answer 2

We see from the figure the ray incident on the second mirror ${{M}_{2}}$ retraces its path (way). This would result the incident ray becomes normally on the second mirrors.Hence the angle between mirros ${{M}_{1}}$ and ${{M}_{2}}$ is $\angle {{M}_{1}}A{{M}_{2}}=30{}^\circ .$