# Homework Help: Variation of saturation photocurrent with intensity

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1. Mar 3, 2015

### enkriya

1. 1. In photoelectric experiment, if anode potential w.r.t. cathode is increased, photocurrent first increases then becomes a constant, since all the photoelctorns ejected from cathode are collected at anode. If we increase the intensity of light at this point, the 'saturation current' increases because number of photons incident per unit time increases. Now the problem is, if we increase the frequncy now keeping the intensity constant, that would mean we are decreasing number of photons incident per unit time, which should result in reduction of current.
Number of photons per unit time = IA/hf .

It is clear that number of photons strking per unit time will decrease, and current must drcrease. However every textbook of physics that i have states that saturation photocurrent will not change when frequncy is changed but intensity is kept constant.

In this graph, frequencies are different but intensity is same. By my logic, saturation current should be different. But is shown to be same for all frequencies.
Any ideas/ solutions are welcome. Thankyou for your time.

2. Mar 3, 2015

### enkriya

Hi rude man (Nice nickname). Thanks for reply. The question is not about photodiodes. It is about photelectric experiment. The results of photoeectric experiment were explained by Einstein's photon model. The experiment completely follows photon energy model.

3. Mar 3, 2015

### rude man

Oh, OK, sorry. Gotta look into this more. Meanwhile, others will undoubtedly help.

Last edited: Mar 3, 2015
4. Mar 3, 2015

### rude man

Could you cite a reference saying what you said? In your graph, are you sure intensity is kept constant?

5. Mar 3, 2015

### rude man

Another thought: The weakest photons will liberate electrons close to the outermost orbital only. But it takes higher-energy photons to lberate electrons with larger bonding energies. So the higher-energy photons liberate electrons not liberatable by the lower-frequency photons. So the lower number of photons per unit time is compensated by the ability of those higher-energy photons to liberate deeper-situated electrons.