The influence of the screen edge curvature very small in magnitude and the screen absorptivity on the positions of fringers in the diffraction pattern from a thin screen has been revealed in the present paper. It has been proved experimentally that the light reflected from optically denser medium not only loses half a wave, but also undergoes a phase shift by π in the direction of wave propagation. The interference between the edge light propagating to the screen shadow and the incident light has been observed whose diffraction pattern is similar to that observed in the classical scheme. The initial phase delay of the shadow edge light was close to 0.5π and was equal to the phase advance at the edge light propagating to the illuminated side. It is shown that the screen edge projection is not the boundary of the rectilinear light propagation. The realistic scheme of formation of the diffraction pattern from the screen has been proposed. The critical angles of deflection of the edge rays from the incident light direction found earlier and being limiting for the linear dependence of the edge wave amplitude on the diffraction angle are shown to be slightly overestimated. The reason for this has been clarified.