The two opposite concepts - multiphoton and effective photon - readily describing the photoelectric effect under strong irradiation in the case that the energy of the incident light is essentially smaller than the ionisation potential of gas atoms and the work function of the metal are treated. Based on the submicroscopic construction of quantum mechanics developed in the previous papers by the author [Phys. Essays vol. 6, 554 (1993); vol. 10, 407 (1997)] the analysis of the reasons of the two concepts discrepancies is led. Taking into account the main hypothesis of those works, i.e., that the electron is an extended object that is not point-like, the study of the interaction between the electron and a photon flux is carried out in detail. A comparison with numerous experiments is performed.