In a photo-electric set up, a point source of light of power 1.6 x 10 w emits mono-energetic photons of energy5.0 eV. The source is placed at a distance of 0.8m from the centre of stationary metallic sphere of work function 2.0 eV and radius 2 x 10*m. m. The efficiency of photoelectron emission is one for every 108incident photons. Assume that sphere is initiallv neutral and photo-electrons are instantly swe 4/6 after emission. (a) Determine the number of away after emission (b) Determine the ratio of photo-clectrons emitted. (c) it is observed that photo electron emission stops after a certain timet, the light source is switched on, why?