Answer
a. $P_{av}= 2.4\times10^{-4}W $.
b. $E_{rms}= 17.4N/C$.
Work Step by Step
a. The power from the laser is spread uniformly over the cross section.
$$P_{av}=IA=(0.800W/m^2) (3.0\times10^{-4}m^2)=2.4\times10^{-4}W $$
b.
$$E_{rms}=\sqrt{\frac{I}{\epsilon_0 c}}$$
$$E_{rms}=\sqrt{\frac{0.800W/m^2}{(8.854\times10^{-12}F/m)(3.00\times10^8m/s)}}= 17.4N/C$$
