Show that the radiation pressure exerted by an EM wave of intensity I on a surface kept in vacuum is I/c.

Question

Philoid · Accepted Answer

Assume that the surface is exposed to electromagnetic radiations. So, all the radiations are allowed to fall normally on the given surface.

Let the intensity of the radiation is I and the area of the surface is A.

So, the energy received by the surface in each second is given by,

E = I. A

So, number of photons received by surface in each second is given by,

For the perfectly absorbing surface,

So, force is given by,

Pressure is given by,