# Critical Angle Problem

1. May 17, 2009

### qszwdxefc

1. The problem statement, all variables and given/known data
The critical angle for a special glass in air is 44 degrees. What is the critical angle if the glass is immersed in water?

2. Relevant equations
sin(critical angle) = 1/index of refraction

index of refraction of air is 1.00
index of refraction of water is 1.333

3. The attempt at a solution
I have no clue where to start that's the problem :S.

Just for reference, the textbook answer is 68 degrees.

Thanks.

2. May 17, 2009

### Staff: Mentor

Hint: That's only true if the surrounding medium has n = 1. (How is the critical angle formula derived?)

3. May 17, 2009

### qszwdxefc

Ah, Snell's Law where $$\theta_2$$ = $$90^\circ$$.

Thanks.

Last edited: May 17, 2009
4. Jun 19, 2009

### Awsom Guy

Have you tried using the eqaution n1sinQ=n2sinQ
by the way the one is just saying its the first refractive index, and the Q is theta.
Maybe you could try this eqaution.
Thanks I hope that helps...