A plane electromagnetic wave is incident on a plane surface of area A, normally and is perfectly reflected. If energy E strikes the surface in time t then force exerted on the surface is ( c= speed of light)

Question

A plane electromagnetic wave is incident on a plane surface of area A, normally and is perfectly reflected. If energy E strikes the surface in time t then force exerted on the surface is ( c= speed of light) (A) (2E/Atc) (B) (E/2c) (C) (2E/ct) (D) Zero

Tardigrade Admin · Accepted Answer

Incident momentum, p=(E/c) For perfectly reflecting surface with normal incidence Δ p=2 p=(2 E /c) ; F =(Δ p/Δ t)=(2 E /c t)

Q. A plane electromagnetic wave is incident on a plane surface of area $A$ , normally and is perfectly reflected. If energy $E$ strikes the surface in time $t$ then force exerted on the surface is ( $c =$ speed of light)

$\frac{2 E}{A t c}$

$\frac{E}{2 c}$

$\frac{2 E}{c t}$

Zero

Incident momentum, $p = \frac{E}{c}$
For perfectly reflecting surface with normal incidence
$Δ p = 2 p = \frac{2 E}{c}$ ;
$F = \frac{Δ p}{Δ t} = \frac{2 E}{c t}$

Q. A plane electromagnetic wave is incident on a plane surface of area A, normally and is perfectly reflected. If energy E strikes the surface in time t then force exerted on the surface is ( c= speed of light)

Atc2E​

2cE​

ct2E​