Photo-Electric Thresholds and Fatigue

Photo-electric fatigue.—Using elements of the highest purity, clean surfaces were prepared, in a vacuum of the order of ${10}^{-6\mathrm{}}$ mm of Hg, by means of an electromagnetic filing device. A linear relation was found between the logarithm of the photo-electric current and the logarithm of the time elapsed since polishing the specimen. The rate of fatigue depends upon the element used and the factors which produce fatigue and, for a given substance, increases numerically as the threshold is approached. Increasing the pressure increases the rate of fatigue. The action of light has a negligible effect.