The Fermat principle ( Fermat’s principle of least time ) is a postulate in geometric optics , according to which light chooses the shortest path between two points. That is, a ray of light moves from a start point to an end point along a path that minimizes travel time (or, equivalently, minimizes the optical path length ). In a more precise formulation [1] : the light chooses one path from the many nearby ones, requiring almost the same time for passage; in other words, any small change in this path does not lead in the first order to a change in travel time.
This principle, formulated in the I century. Geron of Alexandria for the reflection of light, in general, was formulated by Pierre Fermat in 1662 as the most general law of geometric optics. In various specific cases, already known laws followed from it: the straightness of the light ray in a homogeneous medium, the laws of reflection and refraction of light at the boundary of two transparent media.
The Fermat principle is a limiting case of the Huygens-Fresnel principle in wave optics for the case of a vanishingly small wavelength of light.
The Fermat principle is one of the extreme principles in physics .
Notes
- ↑ Feynman R., Leighton R., Sands M. Feynman Lectures in Physics. Volume 3: Radiation. The waves. Quanta. Translation from English (edition 4). - URSS editorial. - ISBN 5-354-00701-1 .
Literature
- Brief Dictionary of Physical Terms / Comp. A. I. Bolsun, rec. M.A. Elyashevich. - Mn. : Higher School, 1979. - S. 364—365. - 416 p. - 30,000 copies.
Links
- Farm principle - an article from the Great Soviet Encyclopedia . Gagarin A.P.