Question
A silver ball of radius 4.8cm is suspended by a thread in a vacuum chamber. Ultraviolet light of wavelength 200nm is incident on the ball for some time during which a total light energy of 1.0×10−7 J falls on the surface. Assuming that on the average, one photon out of ten thousand photons is able to eject a photoelectron, find the electric potential (in terms of 10−1V) at the surface of the ball assuming zero potential at infinity.