A plane electromagnetic wave of intensity 10 Wm−2 strikes a small mirror of area 20 cm2 , held perpendicular to the approaching wave. The radiation force on the mirror will be

6.6 × 10−11 N 1.33 × 10−11 N 1.33 × 10−10 N 6.6 × 10−10 N

1.33 × 10−10 N

Radiation force=momentum transferred per sec by electromagnetic wave to the mirror $=\frac{2S_{av}A}{c}=\frac{2×(10)×(20×10^{-4})}{(3×10^8)}$ $=1.33 × 10^{-10} N$