Physics - Modern Physics Question with Solution | TestHub

In a photoelectric effect set-up, a point source light of power $3.2\times 10^{-3}\mathrm{W}$ emits monoenergetic photons of energy 5.0 eV. The source is located at a distance of 0.8 m from the centre of a stationary metallic sphere of work function 3.0 eV and of radius $8.0\times 10^{-3}\mathrm{m}$. The efficiency of photoelectron emission is one for every $10^6$ incident photons. Assume that the sphere is located and initially neutral and that photo electrons are instantly swept away after emission. Then