What is the effect of (i) intensity of light (ii) potential on photelectric current ?

i) Effect of intensity of light on photoelectric current.
When photo electric effect is taking place, keeping the frequency of incident radiation fixed, if we plot a graph between intensity of incident radiation and photoelectric current, it is found to be a straight line passing through the origin O as shown in Fig. This is because as intensity increases, the no. of photons striking per unit area per second increases and hence correspondingly the no. of photoelectrons emitted increases. 
Hence photoelectric current is directly proportional to the intensity of incident radiation. i$\propto$I

ii) Effect of potential on photoelectric current.
If we increase the positive potential on anode A gradually, it is found that photo electric current also increases till a stage comes when the photoelectric current becomes maximum.
If we increase the positive potential on anode A further, the photoelectric current does not increase.
This maximum value of photoelectric current is called saturation current and corresponds to the case when all the photoelectrons emitted by the cathode C reach the anode A.

Stopping potential:- If we apply a negative potential to anode A wrt. cathode C. The negative anode exerts a retarding force on the emitted photoelectrons due to which photoelectric current decreases. 
At some retarding potential. the photoelectric current becomes zero as no photoelectrons now have sufficient kinetic energy to reach the anode A. This value of retarding potential is called stopping potential or cut-off potential denoted by V₀. Below stopping potential photo- current is zero.
For a given frequency of incident radiation, stopping potential is independent of intensity of incident radiation.