Given:
refractive index: diamond = 2.42 ; air = 1
90° should have been provided in the problem. I encountered similar problem before.
Using Snell's Law: n1*sin(a) = n2*sin(b)
where:
n1 and n2 are the refractive indexes
sin(a) and sin(b) are the corresponding angles.
n1 = 2.42
n2 = 1.00
b = 90°
n1 * sin(a) = n2 * sin(b)
2.42 * sin(a) = 1 * 1
2.42 * sin(a) = 1
sin(a) = 1 / 2.42
sin(a) = 24.4° Choice B.
