Question

Power of point source is 450 watt. Radiation pressure on a perfectly Reflecting surface at a distance of 2 m is

(1) \(2\times 10^{-8}\)

(2) \(4\times 10^{-8}\)

(3) \(6\times 10^{-8}\)

(4) \(8 \times 10^{-8}\)

Answer 1

Correct option is : (3) \(6\times 10^{-8}\) 

\(\frac{2I}{C} = \frac{2}{C} \left(\frac{P}{4\pi r^2}\right)\)

\( = \frac{2\times 450}{3\times 10^8 \times 4\pi 2^2} = \frac{300}{16\pi}10^{-8}\)