A plane electromagnetic wave of wave intensity 6 W/m² strikes a small mirror of area 40 cm², held perpendicular to the approaching wave. The momentum transferred by the wave to the mirror each second will be:

1.6 × 10^–10 kg–m/s

In one second

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

= 1.6 × 10^–10 kg–m/s