The work function concerns the surface photoelectric
effect where the photon is absorbed by an electron in a
band. The theoretical determination of the work function
is the problem of the solid state physics. On the other
hand, there is the so called atomic photoeffect (Amusia,
1987), where the ionization energy plays the role of the
work function. The system of the ionization energies is
involved in the tables of the solid state physics.
The idea of the existence of the Compton effect is also
involved in the Einstein article. He writes (Einstein, 1905)
the possibility should not be excluded, however, that
electrons might receive their energy only in part from the
light quantum. However, Einstein was not sure, that his
idea of such process is realistic. Only Compton proved
the reality of the Einstein statement.
Equation 1 represents the so called one-photon
photoelectric effect, which is valid for very weak
electromagnetic waves. At present time of the laser
physics, where the strong electromagnetic intensity is
possible, we know that the so called multiphoton
photoelectric effect is possible. Then, instead of equation
(1) we can write