What is the force exerted by a photon of intensity 1.4 kWm–2 if it falls on a perfect absorber of radius 2 metre ?
Answer & explanation
Correct answer: option 1
$F_{ex} =\frac{P}{c}=\frac{IA}{c}$
$I = 1.4 × 10^3\, W/m^2$
$A = 4πr^2 = 4 × 3.14 × (2)^2 m^2$
$F_{ex} = 2.35 × 10^{–4} N$