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 $\frac{IRH}{c}$

Here in this case,

Effective area $A=\frac{2RH}{2}$

where triangle of base 2R and height H

Radiation pressure $P=\frac{\text{Intensity}}{\text{Speed}}=\frac{I}{C}$

And hence Radiation Force$=P\times A=\frac{I}{C}\times RH⟹F=\frac{IHR}{C}$