Take your pick. It doesn't make any difference. In both the classical description of an electromagnetic wave and the quantum photon picture there is momentum carried in the laser beam.
It is a bit more tricky in the case of the photoelectric effect and the quantum description describes the phenomenon better. The problem is that there is a minimum energy required to eject a photo-electron and a classical EM wave whose wavelength is too long just can't do it, no matter what the intensity. Einstein figured this out. Check out: for some information.
LeeH
(published on 04/07/2010)
