The Fresnel equations give the ratio of the reflected and transmitted electric field amplitude to initial electric field for electromagnetic radiation incident on a dielectric. In general, when a wave reaches a boundary between two different dielectric constants, part of the wave is reflected and part is transmitted, with the sum of the energies in these two waves equal to that of the original wave. Since electromagnetic waves are transverse, there are separate coefficients in the directions perpendicular to and parallel to the surface of the dielectric. The coefficients for reflection and transmission of the "transverse electric field" (abbreviated "TE") are denoted and , respectively, while the coefficients for reflection and transmission of the "transverse magnetic field" (abbreviated "TM") are denoted and , respectively. In this formulation, a negative sign for an amplitude coefficient denotes a ray in the opposite direction as the incident ray. In addition to the amplitude coefficients, power (or intensity) coefficients are often defined as the square of the corresponding amplitude coefficients, i.e.,

			(1)
			(2)
			(3)
			(4)

Brewster's Angle, Critical Angle, Dielectric, Fresnel Reflection Coefficients, Fresnel Transmission Coefficients, Reflectance, Total Internal Reflection, Transmittance