Özet:
The methods of physical optics and physical theory of diffraction are reviewed for electromagnetic waves. The Fermat principle and its' modified version are investigated and the necessity of the introduction of a variable unit vector is put forth. The scattering integrals of modified theory of physical optics are reviewed in this context. Recent comments on the modified theory of physical optics are discussed and refuted clearly. A proof is given on the nature of the physical theory of diffraction's correction terms. The proof is visualized with some numerical simulations.