Light with energy flux 25 × 10⁴ W·m⁻² falls normally on a perfectly reflecting surface of area 15 cm². Average force exerted is:
Options

Question

Light with energy flux 25 × 10⁴ W·m⁻² falls normally on a perfectly reflecting surface of area 15 cm². Average force exerted is:

G1 Physics · Accepted Answer

For normal reflection pressure is 2I/c. Area A = 15 × 10⁻⁴ m². Force F = 2IA/c = 2 × 25 × 10⁴ × 15 × 10⁻⁴/(3 × 10⁸) = 2.50 × 10⁻⁶ N. Answer: B.