Question

The radiation force experienced by body exposed to radiation of intensity $I$, assuming surface of body to be perfectly absorbing is

• A. $\frac{\pi R^{2}I}{c}$
• B. $\frac{\pi RHI}{c}$
• C. $\frac{IRH}{2c}$
• D. $\frac{IRH}{c}$

Answer 1

The correct option is D $\frac{IRH}{c}$

Radiation pressure when a body is perfectly absorbing is $P=\frac{I}{c}$
Effective area for this case is $A=\frac{1}{2}\left(2R\right)H=RH$
radiation force is
$F_{radiation}=\text{Pressure}\times \text{Area}=\frac{I}{c}\times RH=\frac{IRH}{c}$
(for perfectly absorbing surface)