Answer
About 60 billion watts.
Work Step by Step
Assume the radio waves are emitted equally in all directions, so the intensity at a given distance is the radiated power, divided by the surface area of a sphere. Relate the electric field amplitude to the average intensity, using equation 22–8.
$$\overline{I}=\frac{P_0}{4\pi r^2}=\frac{1}{2}\epsilon_ocE_o^2$$
Solve for the power since we are given the electric field amplitude.
$$P_0=4\pi r^2 \overline{I}=2\pi r^2 \epsilon_o c E_0^2$$
$$P_0=2\pi (0.65m)^2 (8.85\times10^{-12} C^2/(N\cdot m^2))(3.00\times10^8m/s)(3\times 10^6 V/m)^2$$
$$\approx 6\times10^{10}W$$
This is many thousands of times greater than the typical power output of a radio station.
