Basic features of the modified theory of physical optics (MTPO) are discussed on the example of scattering at perfectly reflecting half-planes and wedges. It is shown that violations of the geometrical optics (GO), introduced in this technique, result in the MTPO solutions which do not satisfy the Helmholtz equation. They are incorrect at a finite distance from a scattering object; however it can be considered as sort of approximations for the field at a large distance from an edge and away from the GO boundaries.