A light source, emitting three wavelengths 5000 , 6000 and 7000 has a total power of 10³ Watt and a beam diameter of 0.002 m. The power density is distributed equally amongst the three wavelengths. The beam shines normally on a metallic surface of area 10⁴ m² and having a work function of 1.9 eV. Assuming that each photon liberates an electron, calculate the charge emitted per unit area in one second.