Optical fibers are constructed with a cylindrical core surro

Optical fibers are constructed with a cylindrical core surrounded by a sheath of cladding material. Common materials used are pure silica (n₂ = 1.450) for the cladding and silica doped with germanium (n₁ = 1.465) for the core. What is the critical angle ?_crit for light traveling in the core and reflecting at the interface with the cladding material?

Solution

critical angle = sin^-1( n2/n1)

critical angle = sin^-1(1.450/1.465)

critical angle = 81.79 degree