The pressure exerted by an electromagnetic wave of intensity I(Wm-2) on a non-reflecting surface is (c is the velocity of light):
Answer & explanation
Correct answer: option 3
When a surface intercepts electromagnetic radiation, a force and a pressure are exerted on the surface. As the surface is non-reflecting, so it is completely absorbed and in such case the force is
$F = \frac{IA}{c}$
The radiation pressure is the force per unit area, $P = \frac{F}{A} = \frac{I}{c}$