Q 12-08-234JEE MainJEE Main 2025 (3 Apr, Shift 1)Easy
The radiation pressure exerted by a $450\ \text{W}$ light source on a perfectly reflecting surface placed $2\ \text{m}$ away from it is:
Answer: (C) $6\times10^{-8}\ \text{Pa}$
Treating the source as a point source radiating uniformly, the intensity at $2\ \text{m}$ is
$$I = \frac{P}{4\pi r^2} = \frac{450}{16\pi}\ \text{W/m}^2$$
For a perfect reflector (normal incidence) the pressure is $\dfrac{2I}{c}$:
$$p = \frac{2\times450}{16\pi\times3\times10^8} \approx 5.97\times10^{-8} \approx 6\times10^{-8}\ \text{Pa}$$
Solution by Sreeraj P, M.Sc Physics