The maximum value of the electric energy density in an electromagnetic wave whose electric field has peak value \( E_0 \) is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \( \frac{1}{2}\varepsilon_0E_0^{2} \)
The energy density of an electric field \( E \) is \( u=\frac{1}{2}\varepsilon_0E^{2} \). This holds for the field of any charge configuration, including the field of an electromagnetic wave. In the wave, the electric field oscillates between \( -E_0 \) and \( +E_0 \). So the energy density is maximum where the field has its peak value \( E_0 \).
\( \displaystyle u_{\max}=\frac{1}{2}\,\varepsilon_0E_0^{2} \)
NCERT (2026-27):
Energy Stored in a Capacitor – “… If we define energy density as energy stored per unit volume of space, …
Energy density of electric field, \( u=(1/2)\,\varepsilon_0E^{2} \)\( \qquad (2.73) \)
Though we derived Eq. (2.73) for the case of a parallel plate capacitor, the result on energy density of an electric field is, in fact, very general and holds true for electric field due to any configuration of charges.”