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

Answer:

U = 4.39 J

Explanation:

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

$U = \frac{1}{2}\epsilon_0 E^2 V$

here we know that

$\epsilon_0 = 8.85 \times 10^{-12}$

E = 81.1 V/m

V = volume

$V = (0.0253)(speed \times time)$

$V = (0.0253)(3\times 10^8 \times 19.9)$

$V = 1.51 \times 10^8 m^3$

now from above formula we have

$U = \frac{1}{2}(8.85 \times 10^{-12})(81.1)^2(1.51 \times 10^8)$

$U = 4.39 J$