- Optics. the law that the path taken by a ray of light in going from one point to another point will be the path that requires the least time.
Origin of Fermat's principle
First recorded in 1885–90; named after P. de Fermat
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- physics the principle that a ray of light passes from one point to another in such a way that the time taken is a minimum
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012