Physics
posted by J on .
If the critical angle for light at an interface between certain substances is 54.2 degrees, what is the polarizing angle at this same interface?
I am confused!

Use the critical angle to get the index of refraction ratio, N1/N2
Sin 54.2 = N2/N1 = 0.81106
N1/N2 = 1.233
For the polarizing (Brewster) angle, A
tan A = N2/N1
N2/N1 = 50.1 degrees
See http://en.wikipedia.org/wiki/Brewster's_angle
for detailed explanation 
my book says the answer is 39 degrees..

Right.
arctan N2/N1 = arctan 0.81106 = 39.0 degrees
I failed to use the formula correctly