Question: In an electromagnetic wave, the average energy density is associated(A) With electric field only (B) With magnetic field only(C) Equally with electric and magnetic fields(D) None of these

The correct option is (C) Equally with electric and magnetic fields.

In an electromagnetic wave, both the electric field and the magnetic field oscillate perpendicular to each other and to the direction of wave propagation. The energy carried by the electromagnetic wave is distributed equally between these two fields. The energy density is proportional to the square of the amplitude of both the electric and magnetic fields.

Mathematically, the average energy density (U) of an electromagnetic wave is given by:

U = (1/2) * ε0 * E^2 + (1/2) * (1/μ0) * B^2

where:

ε0 is the vacuum permittivity (electric constant),
E is the electric field amplitude,
μ0 is the vacuum permeability (magnetic constant), and
B is the magnetic field amplitude.
Since both the electric and magnetic fields contribute equally to the energy density, option (C) is the correct answer.