English Dictionary

Fermat's principle

固有名詞

The link between ray optics and wave optics, stating (in its original strong form) that the path taken by a ray between two given points is the path that can be travelled in the least time, or (in a weaker form that is true for all cases) in a time that is "stationary" with respect to variations of the path — so that a deviation in the path causes, at most, a second-order change in the traversal time.

日本語の意味

フェルマーの原理：点と点の間を光が進む経路は、進行するのに必要な時間が最小または停留（微小な変化に対して二次的な変化のみ生じる）となる経路であるという、光線状の光学と波動状の光学を結ぶ原理

Fermat's principle explains why light rays bend at an interface: it states that the path actually taken between two points is the one that makes the travel time stationary (and in simple cases, minimal) with respect to small variations of the path.

フェルマーの原理は、境界で光線が屈折する理由を説明します。すなわち、光が二点間を実際に進む経路は、経路のわずかな変化に対して移動時間が定常（単純な場合には最小）になる経路であると述べています。

意味（1）

The link between ray optics and wave optics, stating (in its original strong form) that the path taken by a ray between two given points is the path that can be travelled in the least time, or (in a weaker form that is true for all cases) in a time that is "stationary" with respect to variations of the path — so that a deviation in the path causes, at most, a second-order change in the traversal time.