Question

The intensity of solar radiation incident at the level of upper atmosphere of the earth is $1.35{\text{kW/m}}^2$. What is the force exerted by this radiation on the solar panel of a satellite, of area $100{\text{m}}^2$. Assume normal incidence and complete absorption.

• A. $4.5\times {10}^{-4}\text{N}$
• B. $4.5\times {10}^{-6}\text{N}$
• C. $2.5\times {10}^{-4}\text{N}$
• D. $2.5\times {10}^{-6}\text{N}$

Answer 1

The correct option is A $4.5\times {10}^{-4}\text{N}$

Force exerted by the radiation is given by, $F=\frac{IA\cos \theta }{c}$

For normal incidence, $\theta =0^{\circ }\text{and}\cos 0^{\circ }=1$

$\therefore F=\frac{IA}{c}=\frac{1.35\times {10}^3\times 100}{3\times {10}^8}$
$=4.5\times {10}^{-4}\text{N}$

Hence, $\left(A\right)$ is the correct answer.