JEE Main · PhysicsMedium

$Which of the following statements is correct regarding the energy density $u$ of an electromagnetic wave in vacuum?$

Show correct answer & step-by-step solution

Correct answer: C — Energy is equally divided between electric and magnetic fields

Solution

The average energy density is

u = u_{E} + u_{B}

. Since

u_{E} = \frac{1}{2} ϵ_{0} E^{2}

and

u_{B} = \frac{B ^{2}}{2 μ _{0}}

, and using

E = c B

and

c^{2} = \frac{1}{μ _{0} ϵ _{0}}

, it follows that

u_{E} = u_{B}