The figure (1) shows the variation of photo current with anode potential for a photo-sensitive surface for three different radiations. Let Ia,Ib and Ic be the  intensities and fa,fb and fc  be the frequencies for the curves a.b and c respectively

It is obvious from the figure (1) that tho stopping potential for curve (a) and (b) is the same. Therefore fa=fb This is because, the stopping potential V0 is frequency dependent h∨−W0=eV0. Here W0  is the work function of the metal. We also know that saturation current is proportional to intensity of the incident radiation. So Ia