A parallel beam of monochromatic light of frequency v is incident on a surface. Intensity of the beam is I and area of the surface is A. Find the force exerted by the light beam on the surface for following cases–
(i) the surface is perfectly absorbing and the light beam is incident normally on it.
(ii) the surface is perfectly reflecting and the light beam is incident normally.
(iii) the surface is perfectly absorbing and the light beam is incident at an angle of incidence `theta`.
(iv) the surface is perfectly reflecting and the light beam is incident at an angle of incidence `theta`.

Answer

(i) `(IA)/(c)` , (ii) `(2IA)/(c)`
(iii) `(Iacostheta)/(c)` , (iv) `(2IAcos^(2)theta)/(c)`