The plane electromagnetic wave of wave intensity 6 W/m2 strikes a small mirror of area 30 cm2 , held perpendicular to the approaching wave . The momentum transferred in kg m/s by the wave to the mirror each second will be

Q: The plane electromagnetic wave of wave intensity 6 W/m2 strikes a small mirror of area 30 cm2 , held perpendicular to the approaching wave . The momentum transferred in kg m/s by the wave to the mirror each second will be

(a) 1.2 × 10-10

(b) 2.4 × 10-9

(c) 3.6 × 10-8

(d) 4.8 × 10-7

Sol: Momentum transferred in one second by EM wave to mirror is

$\large p = \frac{2 I A }{c} $

$\large p = \frac{2 \times 6 \times (30 \times 10^{-4})}{3 \times 10^8} $

= 1.2 × 10-10 kg m/s

Radiation force on mirror = Momentum transferred per second

= 1.2 × 10-10 N