What are Einstein's 3 postulates for Photo electric effect?

[uzman1243]

There are certain conclusions that can be explained by quantum physics about the photoelectric effect:
1) photoelectrons only emitted if frequency>threshold frequency and hence energy of photon> work function
2)Increasing intensity increases no. of photons (and thus photoelectrons provided f>f₀ ) and NOT the kinetic energy

But what are the actual postulates (3) proposed by Einstein?
Something like electron discrete energy packets (i'm not really sure).
Can you help me out

 

[moriheru]

The discrete energy packets where as far as I know originally postulated by Max Planck who found a equation that discribes the black body radiation after Wien and ralley jeans law where thought of. But Einstein cirtenly did work on energy levels, I do not doubt that.

 

[Simon Bridge]

This is the sort of thing that shows up a lot as a homework question; but even if it is not, you will benefit most from finding the answer yourself.
i.e. from any of the online histories of quantum mechanics.
http://www.oberlin.edu/physics/dstyer/StrangeQM/history.html
http://www.particleadventure.org/other/history/quantumt.html
http://en.wikipedia.org/wiki/Quantum_mechanics#History