Spherical glass object with index of refraction N

[leon1127]

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 don't know much about optic... so no where to start at

 

[russ_watters]

What you are describing is the operating principle behind fiber optic communications.

 

[jtbell]

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.