Question

A small​plane mirror​placed at the cente of a s​pherical screen of radius R . A beam of light is falling on the mirror.If the mirror makes n revolutin​per second ,the s​peed of light on the scren after reflection from the mirror will be

Answer 1

$$\begin{gathered} \mathrm{The}\mathrm{reflected}\mathrm{ray}\mathrm{turns}\mathrm{through}\mathrm{angle}2\mathrm{\theta },\mathrm{when}\mathrm{the}\mathrm{mirror}\mathrm{is}\mathrm{turned}\mathrm{through}\mathrm{angle}\mathrm{\theta }. \\ \mathrm{Therefore},\mathrm{rotational}\mathrm{speed}\mathrm{of}\mathrm{the}\mathrm{light}\mathrm{spot}\mathrm{will}\mathrm{be}2\mathrm{n}\mathrm{revolutions}\mathrm{per}\mathrm{second}. \end{gathered}$$