A silica optical fiber (ncore=1.45) is surrounded by a polymer cladding with index 1.40. Light in air is directed toward the flat end of the fiber. What is the largest angle the incident beam can make with the fiber axis in air and still be trapped inside the core by total internal reflection at the core–cladding boundary?
a) 15∘
b) 22∘
c) 8.2∘
d) 33∘