Question

If the electric field and magnetic field of an electromagnetic wave are related as $B=\frac{E}{c}$ where the symbols have their usual meanings and the energy in a given volume of space due to the electric field part is $U$, then the energy due to the magnetic field part will be

• A. $\frac{U}{c}$
• B. $\frac{U}{n^{2}}$
• C. $\frac{U}{2}$
• D. $U$

Answer 1

Answer: (D)

$B=\frac{E}{C}$
Energy due to $E=\frac{1}{2} \varepsilon_{0} E^{2}$
Energy due to $B=\frac{B_{0}{ }^{2}}{2 \mu_{0}}$
$E_{\text {part }}=\frac{U}{2} $
$B_{\text {part }}=\frac{U}{2}$
$E_{\text {part }}=B_{\text {part }}$