2014 AIPMT Electromagnetic WavesRadiation pressure Medium Question 33 of 49 in Electromagnetic Waves

Light with an energy flux of $25\times10^4$ $Wm^{-2}$ falls on a perfectly reflecting surface at normal incidence. If the surface area is 15 $cm^2$, the average force exerted on the surface is:

A $1.25\times10^{-6}$ N
B $2.50\times10^{-6}$ N
C $1.20\times10^{-6}$ N
D $3.0\times10^{-6}$ N

The answer is B.

Solution

Average force $F_{av} = \frac{\Delta p}{\Delta t} = \frac{2IA}{c}$
$= \frac{2\times25\times10^4\times15\times10^{-4}}{3\times10^8} = 2.50\times10^{-6}$ N

Concept Force on a perfect reflector

Electromagnetic Waves in past papers

49 questions from this chapter have appeared across 24 exam years.