A beam of white light is incident normally on a plane surface absorbing `70%` of the light and reflecting the rest. If the incident beam carries 20 W of power, the force exerted by it on the surface is

Options

A. `1.3xx10^(-7)N`
B. `2.6xx10^(-7)N`
C. `1xx10^(-7)N`
D. `3.9xx10^(-7)N`

Answer

A

Explanation

`F=(30)/(100)xx(2P)/(c) +(70)/(100)xx(P)/(c) =1.7(P)/(c)`
`=(1.3xx30)/(3xx10^(8)) =1.3xx10^(-7) N`