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## Main Question or Discussion Point

In fermats principle what if there is more than one path for which the variation in optical path length is stationary.Then which path would light take to reach from one point to another.

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- Thread starter Joyal Babu
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In fermats principle what if there is more than one path for which the variation in optical path length is stationary.Then which path would light take to reach from one point to another.

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Nugatory

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Would you consider light emitted from a point source and being focused by a lens on another point to be an example? The optical path length is the same along all paths through points equidistant from the central axis from source to center of lens to focal point.In fermats principle what if there is more than one path for which the variation in optical path length is stationary.Then which path would light take to reach from one point to another.

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"if there is just one photon and we send it one at a time "

Say again?????

Say again?????

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:),what I meant was we are sending one photon at a time

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Nugatory

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Now you're proposing a variant of the quantum mechanical double slit experiment. If we have detectors along the possible paths, then only one detector will trigger for each photon; if we do not have detectors along the possible paths then it is meaningless to ask about which path each photon follows.

I very very strongly recommend that you nail down your understanding of this problem using classical optics before you jump into the world of quantum mechanics.

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Thank you for that.

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