Question

A small plane mirror placed at the centre of a spherical screen of radius R. A beam of light is falling on the mirror. If the mirror makes n revolution. per second, the speed of light on the screen after reflection from the mirror will be

• A. 4$\pi$nR
• B. 2$\pi$nR
• C. $\frac{nR}{2\pi }$
• D. $\frac{nR}{4\pi }$

Answer 1

The correct option is A 4$\pi$nR

When plane mirror rotates through an angle θ, the reflected ray rotates through an angle 2θ. So spot on the screen will make 2n revolution per second.