Fermat's principle

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Related to Fermat principle: Huygens principle

Fermat's principle

n
(General Physics) 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
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References in periodicals archive ?
The main idea of focusing comes from the Snell's law, which is based on the shortest path principle (Fermat principle).
Nevertheless, Fermat principle is invariant under reparameterising, then parameter "arc length" l may be substituted by optical path, in such a way that dl = [n.sub.r]d[sigma] [15], and a non-singular Lagrangian arises as L = [n.sup.2.sub.r]([bar.r], d[bar.r]/d[sigma]).
Fermat principle would lead to the already known solution: [[??].sub.3] [equivalent to] [bar.t].