Question

In an electromagnetic wave, the electric field of amplitude 6.2 V/m oscillates with a frequency of 2.4 X 10^10 Hz. The Energy density of the wave is __________

(a) 1.4 X 10^-10J/m^3

(b) 2.4 X 10^-10J/m^3

(c) 3.4 X 10^-10J/m^3

(d) 4.4 X 10^-10J/m^3

Answer 1

The correct option is (c) 3.4 X 10^-10J/m^3

Explanation: From Maxwell’s equation, we know, Energy density = εE^2

Here, Emax = 6.2 V/m and ε = 8.85 X 10^-12 C^2/Nm^2

Therefore, Energy Density = 8.85 X 10^-12 X 6.2 X 6.2

= 3.4 X 10^-10J/m^3.