The major drawback of the physical optics (PO) approximation to the solution of scattering problems is that the edge effects can not be taken into account. Therefore, the PO-derived current should be usually corrected by including additional terms that account for diffraction phenomena. In this paper, the effect of the correction terms associated with diffraction on edges of a flat polygonal scatterer, and corresponding to the wedge diffraction is examined. Selected numerical examples demonstrate usefulness and limitations of the approach for analysis of the scattering problems.