In a photoelectric effect set up, a point source of light of power `3.2 xx10^(-3)` W emits monoenergetic photons of energy 5eV.The source is located at a distance of a stationary metallic sphere of work function 3eV and radius `8xx10^(-3)m`.The efficiency of photoelectron emission is one for every `10^(6)` incident photons.Assume that the sphere is isolated and initially neutral and the photoelectrons are initially swept away after emission.
Find the ratio of the wavelength of incident light to the de Broglie wavelength of the fastest phtotelectrons emitted.