Question

A plate is kept in front of a beam of photons. The plate reflects 40% of the perpendicularly incident photons and absorbs the reminder. If the plate absorbs energy at a rate $1200J{s}^{-1}$, find the net force acting cting on it.

Answer 1

Power absorbed by plate , $P=1200J{s}^{-1}$

Also The plate reflects $40\text{\%}$ of the perpendicularly incident photons and absorbs the reminder.

We know that

Force acting on it ,$F=\frac{P}{c}(1+\rho ),$

where $c–$speed of light, $\rho –$ coefficient of reflection, so

$F=\frac{1200}{3\times {10}^8}(1+0.4)=5.6\times {10}^{-6}N$