Answer
$I=1910 W/m^2$
Work Step by Step
The intensity of a ray is equal to the average value of the Poynting vector, which is $$I=S=\frac{E_mB_m}{2\mu_o}$$ Using the relation that $E_m=cB_m$, the equation becomes $$I=\frac{cB_m^2}{2\mu_o}$$ Substituting the value of $B_m=4.0\times 10^{-6}T$ and $c=3.00\times 10^8m/s$ yields $$I=\frac{(3.00\times 10^8m/s)(4.0\times 10^{-6}T)^2}{2(4\pi \times 10^{-7} Tm)}$$ $$I=1910 W/m^2$$
