Fresnelligninger

Fresnelligninger, also known as the Fresnel equations, are a set of equations that describe the reflection and transmission of light (or other electromagnetic waves) when encountering an interface between two different dielectric media. They were derived by Augustin-Jean Fresnel in the early 19th century. These equations quantify the amplitudes of the reflected and transmitted waves in terms of the amplitude of the incident wave, the angle of incidence, and the electromagnetic properties of the two media, specifically their refractive indices.

The Fresnel equations are distinct for two different polarizations of light: s-polarization (perpendicular to the plane of incidence) and p-polarization (parallel to the plane of incidence). For s-polarization, the reflection coefficient depends on the angle of incidence and the ratio of refractive indices. For p-polarization, the reflection coefficient also depends on the angle of incidence and the ratio of refractive indices, but it has a different functional form and exhibits a unique behavior at the Brewster angle, where the reflection coefficient for p-polarized light becomes zero.

The transmission coefficients are related to the reflection coefficients by energy conservation principles. The Fresnel equations are fundamental in optics and electromagnetism, finding applications in various fields such as the design of optical coatings, lenses, and polarizing devices, as well as in understanding phenomena like glare and the appearance of surfaces. They provide a quantitative link between the macroscopic optical properties of materials and the microscopic electromagnetic interactions at an interface.