A parallel beam of the light is incident normally on a plane surface absorbing 40% of the light and reflecting the rest. If the incident beam carries 10 watt power, find the force exerted by it on the surface.

Options

A. `1.11xx10^(-8)N`
B. `2.22xx10^(-8)N`
C. `3.33xx10^(-8)N`
D. `6.66xx10^(-8)N`

Answer

C

Explanation

Here, `lambda=500xx10^(-9) m, P=10W`,
Total momentum per second of the incident light ltbr? `=P/c=10/(3xx10^(8))=3.33xx10^(-8)Ns`
final momentum of incident light `=0`, as the surface is perfectely abosorbing.
Force =rate of change of momentum
`=(3.33xx10^(-8))/(1s)Ns=3.33xx10^(-8)N`