Photoelectric effect: Back to basics

Abstract

The measurement of Planck’s constant by use of the photoelectric effect has long been a cornerstone experiment of the introductory modern physics laboratory. In this paper, the classic experiment is revisited in order to place more emphasis on the physics of the photoemission process. Toward this end, a measurement and theoretical analysis of the quantum yield of a commercial photocell are presented. Near the photoemission threshold, the quantum yield Y is shown to go as (hν−φc)2, where φc is the work function of the metal photocathode. Hence, φc can be determined from an experimental plot of Y1/2 vs hν. In addition, justification is given for a procedure used for many years to determine the stopping potential from a plot of (photocurrent)1/2 versus applied bias voltage.