Physics Help Forum Question on optical pipes and fibers

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 Jul 2nd 2009, 01:34 AM #1 Senior Member   Join Date: Feb 2009 Location: Singapore Posts: 206 Question on optical pipes and fibers I have attached a picture of the question. Number 4, the last part about showing that internal reflection occurs when the angle of incidence meets the required criteria. I'm quite lost on this, would really appreciate if you could provide a good explanation. Thanks! Attached Thumbnails
Jul 3rd 2009, 09:42 AM   #2
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Location: Udupi, Karnataka, India
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 Originally Posted by arze I have attached a picture of the question. Number 4, the last part about showing that internal reflection occurs when the angle of incidence meets the required criteria. I'm quite lost on this, would really appreciate if you could provide a good explanation. Thanks!
n3*sinθm = n2sinr ........(1)
If C is the critical angle between the core and clad, then C = 90 - r
So n1*sinC = n2*sin90
Or n1*sin(90 - r) = n2
Or n1*cosr = n2.........(2)
Square eq.1 and 2 and add. The solve for sinθm.

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