Q 12-08-068JEE MainJEE Main 2024 (31 Jan, Shift 1)Medium
In a plane EM wave, the electric field oscillates sinusoidally at a frequency of $5\times10^{10}\ \text{Hz}$ and an amplitude of $50\ \text{V m}^{-1}$. The total average energy density of the electromagnetic field of the wave is: [Use $\varepsilon_0 = 8.85\times10^{-12}\ \text{C}^2\text{N}^{-1}\text{m}^{-2}$]
Answer: (A) $1.106\times10^{-8}\ \text{J m}^{-3}$
Average total energy density (electric + magnetic):
$$u = \tfrac12\varepsilon_0E_0^2 = \tfrac12\times8.85\times10^{-12}\times2500 \approx 1.106\times10^{-8}\ \text{J m}^{-3}$$
Solution by Sreeraj P, M.Sc Physics