An electromagnetic wave of frequency ( I × 10^ 14 ~Hz ) is...

Given, electromagnetic wave frequency, (f_m=1.0 \times 10^{14} $\mathrm{~Hz}$) amplitude of the electric field, (E_0=4 $\mathrm{Vm}^{-1}$) permittivity of free space, (\varepsilon_0=8.8 \times 10^{-12} $\mathrm{C}^2$\mathrm{~N}^{-1} \mathrm{~m}^{-2}$) The value of energy density (energy/volume) is given by (\therefore \quad$u=\frac{1}{2} \varepsilon_0 E_0^2) Putting the given values, we get ($$\begin{aligned} =\frac{1}{2} \times8.8 \times 10^{-12} \times(4)^2 \mathrm{~J}/ \mathrm{m}^3 =\frac{1}{2} \times8.8 \times 16 \times 10^{-12} \\ \therefore \quad u =70.4 \times 10^{-12} \mathrm{Jm}^{-3} \end{aligned}$$$) Hence, the energy density of the electric field will be (70.4 \times 10^{-12}$\mathrm{Jm}^{-3}).