College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 26

Two light sources are used in a photoelectric experiment to determine the work function for a particular metal surface. When green light from a mercury lamp ( = 546.1 nm) is used, a stopping potential of 0.376 V reduces the photocurrent to zero. (a) Based on this measurement, what is the work function for this metal (b) What stopping potential would be observed when using the yellow light from a helium discharge tube ( = 587.5 nm)