Question

What is the critical angle for light traveling inside the rod??

Answer 1

You need to use snell’s law in this problem. N1sin (theta) = n2sim (theta)

N1 = index of oil

N2 = index of glass

If you already have the numbers, include it in this equation:

N1.sin (90deg) = N2.sin (critical angle) (note sine (90deg) = 1)