Fermat's principle

English Etymology First proposed by French mathematician Pierre de Fermat in 1662. Proper noun en physics optics The principle, which links geometrical optics (or "ray optics") with wave optics, that the path traversed by a ray between two given points is: en in the original "strong" formulation the one that takes the least time, or en in a weaker but more general formulation one that takes a time that is "stationary" with respect to variations of the path (so that, loosely speaking, a small change in the ray path entails a very small change in the traversal time). en 1960 w:John Clarke Slater Quantum Theory of Atomic Structure McGraw-Hill https://books.google.com.au/books?id=DsJEAAAAIAAJ&q=%22Fermat%27s+principle%22&dq=%22Fermat%27s+principle%22&hl=en&newbks=1&newbks_redir=0&sa=X&ved=2ahUKEwiJ_Mu4j5z9AhVIJLcAHVqwDQAQ6AF6BAhDEAI 39 But we now see that, if we use Fermat's principle, a fundamental result of any wave theory, and combine it with de Broglie's assumption about the relation between momentum and wavelength, we are led at once to the principle of least action. en 1968 Petr Beckmann The Depolarization of Electromagnetic Waves Golem Press https://books.google.com.au/books?id=isA8AAAAIAAJ&q=%22Fermat%27s+principle%22&dq=%22Fermat%27s+principle%22&hl=en&newbks=1&newbks_redir=0&sa=X&ved=2ahUKEwiJ_Mu4j5z9AhVIJLcAHVqwDQAQ6AF6BAhGEAI 108 , Keller simply postulates these rays and finds their direction from Fermat's principle adapted to the hypothesis that these rays exist. 1976, Donald E. Tilley, Walter Thumm, Physics for College Students, Cummings Publishing Company, page 558, students wishing to pursue this branch of physics further will find that refraction too can be explained in terms of Fermat's principle. en Fermat's principle of least time principle of least time Translations principle in optics Chinese: Mandarin: cmn 費馬原理 Fèimǎ yuánlǐ French: fr principe de Fermat m German: de Fermatsches Prinzip n Italian: it Polish: pl zasada Fermata f See also en principle of least action en eponyms