In experiment of photoelectric effect collector A is kept at positive potential.
When magnitude of positive potential is increased,photoelectric current also increases.
For particular voltage on plate A,all emitted electrons will reach to collector (A) and current will become maximum.
Now if collector voltage on collector is increased.Photoelectric current will not increase value of this collector current is called saturation current.
For value of given collector potential photoelectric current become constant is called saturation current.
Now collector voltage is sequentially decreased and made negative.
There will be repulsion between electron and negative voltage on collector (A).
When collector voltag is made more negative ,repulsive force will increase and more energetic electrons only will reach to collector.Value of collector current will sequentially decrease rapidly.
value of negative voltage on collector for which photoelectric current become zero is cut off voltage or stopping potential .It is denoted by `V_(0)`.
Energy of all electron emitted from metal surface are not equal.Stopping potential gives idea of maximum kinetic energy of photoelectron.
When photoelectric current become zero maximum kinetic energy of photoelectron `(K_(max))`will be equal to energy of electron at `V_(0)` voltage.
For photoelectric current to become zero maximum kinetic energy of phto electron=energy of electron at `V_(0)` voltage
`K_(max)=eV_(0)`
In this experiment when frequency of incident radiation is kept constant and intensity of radiation is kept costant and intensity of radiation is charge for three different value `I_(1)ltI_(2)ltI_(3)`, graph of photoelectric current versus stopping potential is shown in figure.
Graph shows that with increase in intensity saturation current increases.Thus no. of photo electrons emitted per second increases with increase in intensity of incident radiation.
From graph,it can be said that for given frequency,stopping potential do not depend on intensity.
Thus,maximum kinetic energy of photoelectron depends on frequency of energy of photoelectron depends on frequency of incident radiation but it do not depend on intensity of incident radiation.
