Question

An incident ray strikes a plane mirror at an angle of incidence of ${40}^o$. What is the percentage decrease in the angle of reflection if the incident ray moves to an angle of incidence of ${30}^o$?

• A. $10$%
• B. $20$%
• C. $25$%
• D. $30$%

Answer 1

Answer: (C)

$25$%

According to the laws of reflection, angle of incidence is same as the angle of reflection. So, percentage decrease in the angle of reflection will be same as the percentage decrease in the angle of incidence.

percentage decrease in angle of incidence

$=\frac{{40}^o-{30}^o}{{40}^o}\times 100$

$=25$