Question : The rms value of the electric field of the light coming from the sun is 720 N/C. Then what is the average total energy density of the electromagnetic wave?
Doubt by Parish
Solution :
We know, average energy density of Electric Field in an electromagnetic wave is given by
=½ ε₀Erms²
We also know that total average energy density of the electromagnetic wave is equal to the sum of the average energy densities of electric and magnetic field.
But average energy density of electric field is equal to the average energy density of magnetic field.
So we can write that
Average energy density of electromagnetic wave = 2×Average energy density of
= 2×½ ε₀Erms²
= ε₀Erms²
= 8.85×10-12×(720)²
= 8.85×518400×10-12
= 885×5184×10-12
= 4587840×10-12
= 4.59×10-6 J/m³
