Question

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

• A. $6.4\times 10^{- 7}kgms^{- 1}$
• B. $4.8\times 10^{- 8}kgms^{- 1}$
• C. $3.2\times 10^{- 9}kgms^{- 1}$
• D. $1.6\times 10^{- 10}kgms^{- 1}$

Answer 1

Answer: (D)

In the case of complete reflection, the momentum transfer by the wave to the mirror in each second will be
$P=\frac{2 U}{c}=\frac{2 S_{a v} A}{c}=\frac{2 \times 6 \times 40 \times 10^{- 4}}{3 \times 10^{8}}$
$=1.6\times 10^{- 10}kgms^{- 1}$