Phase Relations for the Electromagnetic Wave Components Reflected from and Transmitted by a Dielectric Layer

An important property of electromagnetic waves, which follows from Fresnel's formulas but has not been clearly defined as yet in the scientific and educational literature, is considered: the phase difference between the wave components reflected from and transmitted through a plane dielectric layer located between optically identical media is equal to /2, irrespective of the optical parameters of the layer and surrounding media, the wavelength, and the wave polarization state.