Answer
See answers.
Work Step by Step
The energy per unit area per unit time is the magnitude of the average intensity, equation 22–8. The area and energy are given, so we find the intensity and solve for the time.
$$\overline{I}=\frac{c}{2\mu_o}(\sqrt{2}B_{rms})^2=\frac{c B_{rms}^2}{\mu_o}=\frac{\Delta U}{A\Delta t}$$
$$\Delta t=\frac{\mu_o\Delta U}{Ac B_{rms}^2}=\frac{(4\pi\times10^{-7})(365J)}{(1.00\times10^{-4}m^2)(3.00\times10^8m/s)(22.5\times10^{-9}T)^2}=3.02\times10^7s$$
