Photoelectric Effect: Frequency vs. Amplitude

[rictor]

How energy of the emitted electron is proportional to the incident light frequency but not to its amplitude according to photoelectric effect?

 

[Drakkith]

Because each ejected electron has only interacted with one photon. Thus the energy depends only on the frequency of that photon. Higher amplitude just means more photons falling onto the material. As far as I know, until you get to really, REALLY high intensities, the kind you can only get from extremely powerful lasers, the chances of an electron interacting with more than one photon at a time is essentially zero.