A beam of light consists of 4 wavelength $\;4000A^{0},4800A^{0},6000A^{0}\; and\;7000A^{0}\;,$ each of intensity $\;1.5\times10^{-3}Wm^{-2}\;.$The beam falls normally on an area $\;10^{-4} m^2\;$ of a clean metallic surface of work function 1.9eV . Assuming no loss of light energy the no.of photoelectrons liberated per second is

Question

$(a)\;1.12\times10^{14}\qquad(b)\;1.12\times10^{136}\qquad(c)\;1.12\times10^{13}\qquad(d)\;1.12\times10^{12}$