For a particular metal, we can conduct the photoelectric experiment with monochromatic light of different frequencies, to obtain the stopping potentials V_s at each frequency f. We now have the necessary data to plot a graph of KE_max (calculated from KE_max = eV_s) against f.

Since , plotting KE_max against f should result in a straight line graph, with the gradient and y-intercept corresponding to h and –Φ respectively.

If we plot one graph for each metal, we will obtain parallel lines, all with gradient equals to h, with graphs of higher work-function metlas sitting lower since the y-intercepts correspond to –V_s.

• 18 Quantum Physics