Physics - Modern Physics Question with Solution | TestHub

In a photoelectric experiment, a parallel beam of monochromatic light with the power of$200\text{W}$is incident on a perfectly absorbing cathode of work function$6.25 \mathrm{eV}$. The frequency of light is just above the threshold frequency so that the photoelectrons are emitted with negligible kinetic energy. Assume that the photoelectron emission efficiency is 100%. A potential difference of$500\text{V}$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$F=n\times {10}^{-4}\mathrm{ N}$due to the impact of the electrons. The value of$n$is __________. Mass of the electron$m_e=9\times {10}^{-31}\mathrm{ kg} \mathrm{a}\mathrm{n}\mathrm{d} 1.0 \mathrm{eV}=1.6\times {10}^{-19}\mathrm{ J}$.