Light Refracted through a Prism

[Yaaaldi]

Homework Statement

Light is incident along the normal to face AB of a glass prism of refractive index 1.66, as shown in the figure.

[PLAIN]http://img175.imageshack.us/img175/6339/yffigure3336.jpg

Find $$\alpha$$max, the largest value of the angle $$\alpha$$ such that no light is refracted out of the prism at face AC if the prism is immersed in air.

Homework Equations

I know I'm supposed to use Snells Law, but I really have no idea how to obtain the answer.

The Attempt at a Solution

I know that the incident angle is equal to 90 - $$\alpha$$ but that's all I know really.

Thanks

 

[Stonebridge]

Yes the angle of incidence is 90-α
I've drawn it in your diagram. (i)

You now need to find what angle i needs to be in order that there is total internal reflection at the hypotenuse face of the prism.
Using Snell's Law, do you know the criteria for total internal reflection?