# The electric field of a plane electromagnetic wave varies with time of amplitude 2 Vm-1 propagating along z-axis…

Q: The electric field of a plane electromagnetic wave varies with time of amplitude 2 Vm-1 propagating along z-axis. The average energy density of the magnetic field is (in Jm-3)

(a) 13.29 × 10-12

(b) 8.86 × 10-12

(c) 17.72 × 10-12

(d) 4.43 × 10-12

Ans: (b)

Sol: Avg mag. Energy density $\Large u_B = \frac{B_0^2}{4 \mu_0}$