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Number of reflections in an Optical fibre

  1. May 6, 2014 #1
    How many reflections will be made by a light entering a 2m long optical fibre cable. If the angle of incidence with the axis of the core is 3.43° . Given that the core diameter and refractive index are 60μm and 1.48 respectively

    I got the answer as 36368.48 is this correct?



    sinθ= n(air)/n(fibre) = 0.67567

    ∴ θ= 42.50664°

    tanθ= 0.9165
    ∴No. of reflections = L/(d tan θ )
    = 36368.48
    Last edited: May 6, 2014
  2. jcsd
  3. May 6, 2014 #2


    User Avatar

    Staff: Mentor

    Hi Rahulr2k. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    I would have thought that the refractive index is irrelevant, other than needing to be sufficient to ensure that there is total internal reflection?

    Does that 3.43 figure have units of degrees?
    Last edited by a moderator: May 6, 2017
  4. May 6, 2014 #3
    yes...3.43 degrees
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