Question

A plane electromagnetic wave of wave intensity 6 $W/m^2$strikes a small mirror area 40 $c{m}^2$, held perpendicular to the approaching wave. The momentum transferred by the wave to the mirror each second will be

• A. $6.4\times {10}^{-7}kg-m/s^2$
• B. $4.8\times {10}^{-8}kg-m/s^2$
• C. $3.2\times {10}^{-9}kg-m/s^2$
• D. $1.6\times {10}^{-10}kg-m/s^2$

Answer 1

The correct option is D

$1.6\times {10}^{-10}kg-m/s^2$

Momentum transferred in one second

$p=\frac{2U}{c}=\frac{2S_{av}A}{c}=\frac{2\times 6\times 40\times {10}^{-4}}{3\times {10}^8}$

$=1.6\times {10}^{-10}kg-m/s^2$.