The Shot Effect in Photoelectric Currents

Abstract

The shot effect, as it occurs in a photoelectric current, has been used to secure an evaluation of the electron charge. A new and original method of amplifier calibration, which involved the use of a modulated light beam, simplified the measurements and the computation of the result. In the absence of space charge, the experimental value of the electron charge was 1.61×${10}^{-19\mathrm{}}$ coulombs for a thermionic current, and about 25 percent greater for a photoelectric current. It was found that the shot effect is enormously increased in photoelectric currents which are amplified by collision ionization. Statistical variations which might be expected to occur in a beam of radiant energy could not be detected, since, within the limits of experimental accuracy, the shot effect in photoelectric currents was found to be independent of the frequency of the light producing electron emission.