A traveling electromagnetic wave in a vacuum has an electric field amplitude of 72.7 V/m. 72.7 V/m. Calculate the intensity S S of this wave. Then, determine the amount of energy U U that flows through area of 0.0211 m 2 0.0211 m2 over an interval of 10.3 s, 10.3 s, assuming that the area is perpendicular to the direction of wave propagation.

a) 7.02 W/m²

b) 1.53 J

Explanation:

Given

Amplitude of the electric wave, = 72.7 V/m

Area of flow, A = 0.0211 m²

Time taken, t = 10.3 s

To calculate the Intensity, S. We use the formula

I = E (rms) ² / (cμ), where

E (rms) = E / √2 = 72.7 / √2

E (rms) = 72.7 / 1.4142

E (rms) = 51.41

c = 2.99*10^8

μ = 1.26*10^-6

I = 51.41² / [ (2.99*10^8) (1.26 x 10^-6) ]

I = 2642.99 / 376.74

I = 7.02 W/m²

U = energy = IAt

U = (7.02) * (0.0211) (10.3) J = 1.53 J