Optic fiber

  • Thread starter topsaa
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I got this question in a practice midterm and i can't seem to even start this problem, i tried using my text book (university physics) and nothing to be found in there either.

Does anyone know start this problem?

so we were able to to get part a and b.

on part c we were able to get the time taken for light to travel in air but what would be the difference of the light travelling inside the fiber? does it slow down?
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a) From the geometry you can also get the number of times it bounces in terms of N - just work out the length of one bounce in 'n' and angle.


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The triangle shown on the diagram will help you to calculate the length of the 'long route' compared with the 'direct route'. Hint: you can ignore the multiple reflections - just assume the fibre is as broad as you want and work it out for one huge triangle! The distances involved will be the same.
The refractive index of the glass tells you the ratio of speed in air and in the fibre.
There's loads in every textbook about critical angle and how to find it from the refractive index.
I don't think you should need any more help. Get your thinking cap on.

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