One
I'm assuming (perhaps incorrectly) that the ray is coming in perpendicularly to the surface of the crown glass. The question is a bit ambiguous, so the assumption may not be correct.
If I am correct.
Formula
n1*sin(θ1) = n2*sin(θ2)
Givens
n1 = 1
n2 = 1.52
θ1 = 90 degrees.
θ2 = ?
Solution
1 * 1 = 1.52 * sin(θ2)
1/1.52 = sin(θ2)
0.6578 = sin(θ2)
θ2 = sin-1(0.6578)
θ2 = 41.14 degrees.
Two
The critical angle is the one that produces 90o as the exit point. The formula is the same for this question as it was for the first question
Givens
n1 = 1.473
n2 = 1.33
θ1 = ?
θ2 = 90o
Solution
1.473 sin(θ1) = 1.333 Sin(90)
sin(θ1) = 1.333 / 1.473 * 1
sin(θ1) = 0.90496
θ1 = sin-1(0.90496)
θ1 = 64.82 degrees
