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Fermat's Principle

by manimaran1605
Tags: fermat, principle
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manimaran1605
#1
Jul24-14, 05:58 AM
P: 58
The expression gives time taken to reach a a distance ds in a medium.
The expression has the dimension of time, But my question is how come the denominator is (c/n)? why it can't be (cn)? explain me.
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sophiecentaur
#2
Jul24-14, 06:18 AM
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Bearing in mind that the speed through a medium must always be less than c and that refractive index is always specified such that it is greater than unity. Using c/n produces the sensible answer, which is that light will always take longer to travel through a medium than through a vacuum.
IF n were defined the other way round, then your alternative would apply.


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