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13 Nov 2011 14:57:41 IST

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Why refraction occur due to change in speed of light or going from one medium to another?

Physics

Why refraction occur due to change in speed of light or going from one medium to another?

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abhijit dutta

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13 Nov 2011 19:36:06 IST

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Oh I totally love this question. Reflection ,refraction or any other geometrical phenomenon of light is actually goverened by a basic principle that light like any other natural entity wants to do any job in the minimum possible time. This is formally known as fermat's theorem. Reflection laws of i = r is also very trivially derived from the minimum time theory. The refractive law we call snell's law is also derived trivially using the minimum time condition keeping in mind that the speed of light is going to change when light changes medium.

abhijit dutta

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13 Nov 2011 19:37:54 IST

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If anyone wants a more detailed explanation of this or want to see how i=r and snell's law are proved very easily using fermat's theorem and basic geometry ...please mail me , I will send illustrated proof and detailed explanation.Email at abhimania@gmail.com

edison

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28 Jan 2012 12:49:31 IST

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Fermat's Principle:Reflection

Fermat's Principle: Light follows the path of least time. The law of reflection can be derived from this principle as follows:

The pathlength L from A to B is

Since the speed is constant, the minimum time path is simply the minimum distance path. This may be found by setting the derivative of L with respect to x equal to zero.

This derivation makes use of the calculus of max-min determination, the derivative of a square root, and the definitions of the triangle trig functions.

Fermat's Principle and Refraction

Fermat's Principle: Light follows the path of least time. Snell's Law can be derived from this by setting the derivative of the time =0. It shows how the refraction of light at an interface depends upon the indices of refraction.

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