Question

A traveling electromagnetic wave in a vacuum has an electric field amplitude of 81.1 V/m. Calculate the intensity S of this wave. Then, determine the amount of energy U that flows through the area of 0.0253 m^2 over an interval of 19.9 s, assuming that the area is perpendicular to the direction of wave propagation.

Answer 1

U = 4.39 J

Step-by-step explanation:

Electric field energy stored in the medium or vacuum is given as

`U = (1)/(2)\epsilon_0 E^2 V`

here we know that

`\epsilon_0 = 8.85 * 10^(-12)`

E = 81.1 V/m

V = volume

`V = (0.0253)(speed * time)`

`V = (0.0253)(3* 10^8 * 19.9)`

`V = 1.51 * 10^8 m^3`

now from above formula we have

`U = (1)/(2)(8.85 * 10^(-12))(81.1)^2(1.51 * 10^8)`

`U = 4.39 J`