Effect of frequency on stopping potential

Previously,in my blog I have mentioned effect of potential on photocurrent.Now I am going show you effect of frequency on stopping potential

Here from the above graph you can observe that different values of stopping potential are obtained on varying the frequency of incident light but one thing that remains constant is the photocurrent.The stopping potential is more negative for higher frequencies of incident light.This further reinstates that greater is the frequency of incident light ,greater is the maximum kinetic energy of photoelectrons and thus we need greater retarding potential to stop them completely.

Now the question is what did we learn from all this experiments.The answer is that we have learned the basic laws of photoelectric emission which are as follows:-

• There is certain minimum frequency of radiation known as threshold frequency,such that if the radiation of incident light has frequency below that of threshold frequency then no one in the world can make photoelectric emission occur irrespective of however intense is the radiation and the damn time you can give.
• Now if the frequency of incident light is greater than the threshold frequency,then photoelectric current is directly proportional  to the intensity of incident radiation till a saturation is reached .
• For the incident frequency greater than the threshold frequency ,the maximum kinetic energy of the photoelectrons is directly proportional to the frequency of incident radiation and is independent of both the intensity and the duration of exposure.
• Photoelectric emission is an instantaneous process.The time interval of falling of radiation and ejection of photoelectrons is of the order of 10^-9 sec.