Question

a plane electromagnetic wave is normally incident on a plane surface of area A and is perfectly reflected. if the average pressure exerted on the surface is P the energy exerted on the surface in time t is

Answer 1

Answer:

The answer will be PctA/2

Explanation:

According to the problem the area of the surface is given as A and the average pressure on the surface is P

We know that the incident momentum , m = E/c

For the perfect reflection,

Δm = 2m = 2E/c [ where E is the energy exerted]

Now force , F = Δm/Δt = 2E/ct

Now it is given that the average pressure is P

P = F/A =2E/ct/A

=>E = PctA/2