Question

Electromagnetic wave of intensity $1400W/m^2$ falls on metal surface on area $1.5m^2$ is completely absorbed by it. Find out force exerted by beam.

• A. $14\times {10}^{-5}N$
• B. $14\times {10}^{-6}N$
• C. $7\times {10}^{-5}N$
• D. $7\times {10}^{-6}N$

Answer 1

The correct option is D $7\times {10}^{-6}N$

For a perfectly absorbing surface,

$F=\frac{IA}{C}$

$=\frac{(1400w/m^2\times 1.5m^2)}{(3\times {10}^{8}m/s)}$

$=7\times {10}^{-6}N$.