# KEmax vs f Graphs

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

Since $K{{E}_{\max }}=hf-\Phi$, plotting KEmax 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 –Vs.