A beam of light has two wavelengths $\;4972A^{0}\;$ and $\;6216A^{0}\;$ with a total intensity of $\;3.6 \times 10^{-3} \;Wm^{-2}\;$ equally distributed among the two wavelengths . The beam falls normally on the area of $\;1\;cm^{2}\;$ of a clean metallic surface of work function 2.3 eV.Assume that there is no loss of weight by reflection and that each capable photon ejects one electron .The number of photo electrons liberated in 2s is approximately :

Question

$(a)\;6 \times 10^{11} \qquad(b)\;9 \times 10^{11} \qquad(c)\;11 \times 10^{11} \qquad(d)\;15 \times 10^{11} $