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.