Answer
1.7 V/m.
Work Step by Step
The intensity is the power per unit area. The satellite’s microwave power is distributed uniformly over the circular area specified in the problem.
The energy per unit area per unit time is the magnitude of the average intensity, equation 22–8. Find the rms value of the electric field.
$$\overline{I}=\frac{P}{A}=\frac{1}{2}\epsilon_ocE_o^2=\frac{1}{2}\epsilon_oc(\sqrt{2}E_{rms})^2=\epsilon_ocE_{rms}^2$$
$$E_{rms}=\sqrt{\frac{\overline{I}}{\epsilon_oc }}=\sqrt{\frac{P}{A\epsilon_oc }}$$
$$E_{rms}=\sqrt{\frac{13\times10^3 W }{(\pi (750m)^2) (8.85\times10^{-12} C^2/(N\cdot m^2))(3.00\times10^8m/s) }}$$
$$\approx 1.7V/m$$