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Spherical glass object with index of refraction N

  1. Nov 15, 2005 #1
    imagine there is a spherical glass object with index of refraction N
    is that possible that for some N and angle of incidence A, the light will be total internal reflected forever. In other word, the light will travel within the object forever?
    i have been trying to proof it. but i dont know much about optic.... so no where to start at
    Last edited: Nov 15, 2005
  2. jcsd
  3. Nov 15, 2005 #2


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    Staff: Mentor

    What you are describing is the operating principle behind fiber optic communications.
  4. Nov 15, 2005 #3


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    Staff: Mentor

    For a cylindrical object with light coming in one end, yeah... but for a spherical object there's no incident angle that causes the light to be trapped permanantly inside.

    Leon, all you need for this is Snell's Law for refraction of a light ray, and a bit of geometry. Note that the angle of the ray after the first refraction (entering the sphere) has a certain maximum value, no matter what the incident angle is. That would be a good starting point for a proof.
    Last edited: Nov 15, 2005
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