An optical fiber is to be constructed with a cladding index of refraction n2=1.40. To guarantee that all rays hitting the core–cladding boundary at angles up to 35∘ (measured from the normal inside the core) undergo total internal reflection, what is the minimum allowable index of refraction for the core n1?
a) 1.71
b) 3.00
c) 2.44
d) 2.00