angle of an emerging ray through two boundaries

[nation_unknown]

Thank-you for taking the time to read my problem. I am currently doing work with light and boundaries and have come accross a question that I am having a hard time understanding. I know how to calculate angles when they go through one boundry but I can not figure out how to do it when there is 2 boundaries.

Look at the diagram. Calculate the angle of the emerging ray in air. Assume that the first and second boundaries are parallel.
Diagram: click here (http://img27.imageshack.us/img27/6221/scan.jpg)
(thanks to http://www.imageshack.us/ for the free image hosting)

I understand the question well. The ray is in air, crosses the boundary into the diamond, and then crosses the second boundary back into air where I have to figure out the angle. Where I am stumped is that second boundary. Thank-you for any help you may be able to give me.

[Doc Al]

Apply Snell's law of refraction at each boundary. Question/hint: if the angle of refraction of the light after crossing the first boundary is \theta_2, what will be the angle of incidence of that light before crossing the second boundary?

[nation_unknown]

Thank-you very much for your help. It was able to give me a good start into the question. :).