In a plane EM wave, the electric field oscillates sinusoidally at a frequency of 5 1010 Hz and an amplitude of 50 Vm-1. The total average energy density of the electromagnetic field of the wave is : [Use 0=8.85 10-12 C2/Nm2 ]
- 4.425 10-8 Jm-3
- 2.212 10-10 Jm-3
- 2.212 10-8 Jm-3
- 1.106 10-8 Jm-3
Answer
(4) 1.106 10-8 Jm-3
Solution
uav= 14 0E02+ 14 B02 0= 12 0E02
electric and magnetic fields carry equal average energy; the frequency is not needed
uav= 12 8.85 10-12 (50)2
=1.106 10-8 Jm-3
Answer: (4)