Which angle goes with which refractive index in Snell's law?

[moondawg]

Homework Statement

Snells Law of refraction

Homework Equations

The Attempt at a Solution

n1sinx=n2sinx is an extremely easy equation but i get confused as to which sinx to put my n's to and viseversa. can someone explain to me please?!

 

[Delphi51]

Look at the diagram and formula here
http://en.wikipedia.org/wiki/Snell's_Law
You put a 1 on one medium and a 2 on the other.
Then use the formula that has 1's and 2's on the n's and the θ's.