Answer
$d = 7.3\times 10^{15}~m$
Work Step by Step
We can find the required intensity:
$I = \frac{1}{2}~E_0^2~\epsilon_0~c$
$I = \frac{1}{2}~(\frac{B_0}{c})^2~\epsilon_0~c$
$I = \frac{B_0^2~\epsilon_0}{2c}$
$I = \frac{(1.0\times 10^{-6}~T)^2~(8.854\times 10^{-12}~F/m)}{(2)(3.0\times 10^8~m/s)}$
$I = 1.476\times 10^{-32}~W/m^2$
We can find the required distance:
$I = \frac{P}{4\pi~d^2}$
$d^2 = \frac{P}{4\pi~I}$
$d = \sqrt{\frac{P}{4\pi~I}}$
$d = \sqrt{\frac{10~W}{(4\pi)~(1.476\times 10^{-32}~W/m^2)}}$
$d = 7.3\times 10^{15}~m$
