# At what angle does the light leave the glass

1. Mar 31, 2009

### phys62

1. The problem statement, all variables and given/known data
The drawing shows a rectangular block of glass (n = 1.52) surrounded by a liquid with n = 1.79. A ray of light is incident on the glass at point A with a 30.0° angle of incidence. At what angle does the ray leave the glass at point B?

http://edugen.wiley.com/edugen/courses/crs1507/art/qb/qu/c26/ch26p_18.gif

2. Relevant equations
n1*sin(theta1)=n2*sin(theta2)

3. The attempt at a solution
I solved this and got the right answer by doing the steps below, however I have no idea why I put 1 in the denominater, and this is not the correct way to solve it because my friend's problem is not working out. Please help me figure out the proper way to solve this, as I've tried everything I can think of!

sin(theta2) = (1.6 sin30)/1 = 53.13 degrees

2. Mar 31, 2009

### tiny-tim

Hi phys62!
Where did 1.6 come from?

Show us your full calculations, and then we'll know how to help.

3. Mar 31, 2009

### Staff: Mentor

You need to apply Snell's law twice: Once at A; once at B. And you need to relate the angle of refraction at A to the angle of incidence at B.