일률은

\displaystyle P = S_{\mathrm{avg}} \times A = S_{\mathrm{avg}} \times \pi r^2

입니다. 반지름은

\displaystyle r = 1.0 \times 10^{-3}\ \mathrm{m}

이므로,

\displaystyle P = (4.0 \times 10^4\ \mathrm{W/m^2}) \times \pi (0.0010\ \mathrm{m})^2 \approx 0.126\ \mathrm{W}