# Philosophy Lexicon of Arguments

Author Item Excerpt Meta data
Feynman, Richard

Books on Amazon
Principles I 355
Principle/Theory/Feynman: Principles can explain laws. According to what principle should the law of Snellius be clear at all?
I 355
Fermat's Principle of the Shortest Time/Refraction/Foucault: from all possible paths the light could take, it takes the path that requires the shortest time.
I 356
The path that leads to the object is chosen, if the mirror had not been present. (~).
I 357
Refraction: Transition from air to water: e.g. (Feynman): Suppose someone stands on the shore and sees someone falling from a boat into the water.
We can run much faster than we can swim. Therefore, we should choose a path with a longer route on land than the distance in the water. Exactly the same as light does!
Important: there is an area near the optimum point where, in the first approximation, there is no significant change in time. But in the second order.
I 358
When the ratio of the speed is n, light should penetrate at such an angle that the ratio of the sinuses of the angles Θi und Θr is the ratio of the velocities of the two media.
sin Θi = n sin Θr.
I 358
Principle of the Shortest Time/Fermat/Feynman: Conclusions:
1) Reversibility of direction.
2) E.g. the glass block displaces the beam parallel, since the exit angle is equal to the entrance angle.
E.g. sunset: the light moves slower in the denser air on the ground. The light therefore chooses the shorter path by an acute angle at the entrance. This means that we can still see the sun, even when it has already gone down.
I 359
Bsp mirage
I 361
Analogy/Analog/Theory/Principle of the Shortest Time/Fermat/Identity/Physics/Feynman: apparently, the principle of the shortest time and the statement that angles are equal in reflection, and that the sinuses are proportional to the angles at refraction, are the same.

Fey
R. Feynman
Vom Wesen physikalischer Gesetze München 1993

Fey I
R. Feynman
Vorlesungen über Physik I München 2001

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Ed. Martin Schulz, access date 2017-04-25