In an experimental set up to study the photoelectric effect a point source of light of power 3.2 mW is used. The source emits mono energetic photons of energy 5 eV and is located at a distance d = 0.8 m from centre of a stationary metallic sphere of work function W = 3.0 eV. The radius of the sphere is R = 8 mm. Assume that the sphere is isolated and photo electrons are instantly swept away after emission. Also assume that the efficiency of photoelectric emission is one for every $$10^6$$ photons. In the present set up