Question

The ratio between electric field energy density and magnetic field energy density of an electromagnetic wave, in its region is:

• A. \( 1:1 \)
• B. \( 1:c^2 \)
• C. \( 1:c \)
• D. \( c:1 \)

Hint:

In an electromagnetic wave, the energy densities of the electric and magnetic fields are equal. The ratio of their energies is 1:1.

Answer 1

The Correct Option is A

For an electromagnetic wave, the electric and magnetic energy densities are equal. The energy densities are given by: \[ u_E = \frac{\epsilon_0 E^2}{2}, \quad u_B = \frac{B^2}{2 \mu_0} \] Since the speed of the wave \( c = \frac{1}{\sqrt{\mu_0 \epsilon_0}} \), we have: \[ E = cB \] Thus, the ratio of electric field energy density to magnetic field energy density is: \[ \frac{u_E}{u_B} = 1 \]