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Q.
The pressure exerted by an electromagnetic wave of intensity $I\left( W / m ^{2}\right)$ on a non-reflecting surface is $[c$ is the velocity of light]
Dual Nature of Radiation and Matter
Solution:
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 $F=\frac{I A}{c}$ where $I$ is intensity of light.
$A$ is area of surface and $c$ is velocity of electromagnetic wave.
The radiation pressure is the force per unit area
i.e., $P=\frac{F}{A}=\frac{I}{c}$