Q. A plane electromagnetic wave of intensity 10 $Wm^{- 2}$ strikes a small mirror of area $20\ cm^{2}$, held perpendicular to the approaching wave. The radiation force on the mirror will be
A) $6.6 \times 10^{- 11}\ N$
B) $1.33 \times 10^{- 11}\ N$
C) $1.33 \times 10^{- 10}\ N$
D) $6.6 \times 10^{- 10}\ N$
Explanation
(c) Radiation force=momentum transferred per sec by electromagnetic wave to the mirror
$= \frac{2S_{av}A}{c} = \frac{2 \times (10) \times (20 \times 10^{- 4})}{(3 \times 10^{8})}$
$= 1.33 \times 10^{- 10}\ N$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.