An optical fiber is constructed with a transparent core surrounded by a cladding material. The cladding index of refraction is nclad=1.46. During operation, rays already confined to the core strike the core–cladding boundary at an internal angle of 75∘ measured from the normal.
(a) Determine the minimum possible index of refraction of the core that will ensure total internal reflection for these 75∘ rays.
(b) If the manufacturer instead selects a core material with index 1.60, compute the corresponding critical angle at the core–cladding boundary.
(c) Explain, without further calculation, how decreasing the internal incidence angle of the rays (while keeping the indices fixed) affects the ability of the fiber to confine light.