A certain fiber-optic cable has a core index of refraction

Question

1. Name two conditions for a P_LL to acquire lock.

2. A certain fiber-optic cable has a core index of refraction of 1.43 and a cladding index of refraction of 1.40. Determine the critical angle.

3. A certain fiber-optic cable has a core index of refraction of 1.55 and a cladding index of refraction of 1.35. If a light ray strikes the core/cladding boundary at an angle of 28.2°, will it be reflected or refracted?