The magnetic field of a beam emerging from a filter facing a flood light is given by $B = 12 \times 10^{-8} \sin (1.20 \times 10^7\;z -3.60 \times 10^{15}t)T$ What is the average intensity of the beam ?

Question

$\begin{array}{1 1} 1.71 \times 10^{-2} w/m^2 \\ 17.1\;w/m^2 \\ 1.71\;w/m^2 \\ 0.171\;w/m^2 \end{array}$