Question

A silicon optical fiber with a care diameter large enough has a core refractive index of 1.50 and cladding refractive index 1.47. The critical angle at the core cladding interface is __________. 

(A) 87.5° 

(B) 78.5° 

(C) 38.5° 

(D) 45°

Answer 1

The correct option is (B) 78.5°.

Explanation:

n₁ = core refractive index = 1.5 

n₂ = cladding refractive index = 1.47 

Critical angle θ = sin^–1 (n₂ / n₁) = sin^–1 [(1.47) / (1.5)] = 78.5°