Q. 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) $\frac{nR}{4\pi}$
Explanation
(a) When plane mirror rotates through an angle $\theta$, the reflected ray rotates through an angle $2\theta$. So spot on the screen will make $2n$ revolutions per second
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.