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Augustin-Jean Fresnel [Note 1] (10 May 1788 – 14 July 1827) was a French civil engineer and physicist whose research in optics led to the almost unanimous acceptance of the wave theory of light, excluding any remnant of Newton's corpuscular theory, from the late 1830s [3] until the end of the 19th century.
In 3D computer graphics, Schlick’s approximation, named after Christophe Schlick, is a formula for approximating the contribution of the Fresnel factor in the specular reflection of light from a non-conducting interface (surface) between two media. [1]
The Fresnel equations (or Fresnel coefficients) describe the reflection and transmission of light (or electromagnetic radiation in general) when incident on an interface between different optical media.
Reflectivity is the square of the magnitude of the Fresnel reflection coefficient, [4] which is the ratio of the reflected to incident electric field; [5] as such the reflection coefficient can be expressed as a complex number as determined by the Fresnel equations for a single layer, whereas the reflectance is always a positive real number.
Fresnel lenses are used as simple hand-held magnifiers. They are also used to correct several visual disorders, including ocular-motility disorders such as strabismus. [73] Fresnel lenses have been used to increase the visual size of CRT displays in pocket televisions, notably the Sinclair TV80. They are also used in traffic lights.
Unlike lenses or curved mirrors, zone plates use diffraction instead of refraction or reflection. Based on analysis by French physicist Augustin-Jean Fresnel, they are sometimes called Fresnel zone plates in his honor. The zone plate's focusing ability is an extension of the Arago spot phenomenon caused by diffraction from an opaque disc. [2]
In regular reflection, the Fresnel equations describe the physics, which includes both reflection and refraction, at the optical boundary of a plate. A "pile of plates" is still a term of art used to describe a polarizer in which a polarized beam is obtained by tilting a pile of plates at an angle to an unpolarized incident beam.
The arbitrary assumptions made by Fresnel to arrive at the Huygens–Fresnel equation emerge automatically from the mathematics in this derivation. [13] A simple example of the operation of the principle can be seen when an open doorway connects two rooms and a sound is produced in a remote corner of one of them.