A beam of white light is incident normaly on a plane surface absorbing 70% of the light and reflecting the rest. If the incident beam carries 10 w of power, find the force exerated by it on the surface.

Answer

A, C, D

Explanation

See the hint of above example.
if surface is perfectly absorbing, force is `(P)/(c ).` if
surface is perfectly reflecting then force will be
`(2P)/(c ).`
In this case,
`F = (0.7P)/(c ) + (0.3)((2P))/(c ) = (1.3P)/(c ).`