Solution
= Solution
For isotropic radiation, the average power is spread over a sphere. At $r=0.10\ \mathrm m$, the <intensity of an isotropic radiator> is
$$
\langle|S|\rangle=\frac{P}{4\pi r^2}
=\frac1{4\pi(0.10)^2}
\simeq7.96\ \mathrm{W\,m^{-2}}.
$$
Using the result of part (d),
$$
\boxed{|E_0|=\sqrt{\frac{2\langle|S|\rangle}{\epsilon_0c}}
\simeq77\ \mathrm{V\,m^{-1}}.}
$$