AIIMS 2018 Physics Energy Density MCQ Question

To find the average energy density corresponding to the maximum electric field in an electromagnetic wave, we first determine the maximum magnetic field $B_0 = 200 \times 10^{-6} \, \text{T}$. The maximum electric field $E_0$ can be calculated using the relation $E_0 = cB_0$, where $c$ is the speed of light ($\approx 3 \times 10^8 \, \text{m/s}$). This gives $E_0 \approx 6 \times 10^1 \, \text{V/m}$. The average energy density $u$ in an electromagnetic wave is given by $u = \frac{1}{2} \epsilon_0 E_0^2 + \frac{1}{2} \frac{B_0^2}{\mu_0}$, which simplifies to $u = \frac{1}{2} \epsilon_0 E_0^2$ for average energy density calculations. Substituting the values results in $u \approx 0.016 \, \text{J/m}^3$, matching option C. Other options are incorrect as they do not correspond to the calculated average energy density.