Dual Nature of Radiation

In a photoelectric experiment a parallel beam of monochromatic light with power of 200W is incident on a perfectly absorbing cathode of work function 6.2eV The frequency of light is just above the thres hold frequency so that the photoelectrons are emitted with negligible kinetic energy. Assume that the photoelectron emission efficiency is 100%. A potential difference of 500V is applied between the cathode and the anode. All the emitted electrons are incident normally on the anode and are absorbed. The anode experiences a force F=n×10−4N due to the impact of the electrons. The value of n is_______ . Mass of the electron me=9×10−31kg and 1.0eV=1.6×10−19J