Answer
$p_r = 5.9\times 10^{-8}~Pa$
Work Step by Step
We can use Equation (33-34) to find the radiation pressure:
$p_r = \frac{I}{c}$
$p_r = \frac{P}{A~c}$
$p_r = \frac{P}{4\pi~r^2~c}$
$p_r = \frac{500~W}{(4\pi)(1.5~m)^2(3.0\times 10^8~m/s)}$
$p_r = 5.9\times 10^{-8}~Pa$
