Refraction, reflection, and total internal reflection?

Question

Figure 1 shows a specially constructed tank, containing a layer of air at the bottom, a layer of glass and a layer of water on top. A light source is immersed in the water.
The beam of light is rotated to a certain angle of incidence, as such it no longer passes through the whole container. Explain the phenomenon that casues this to happen and calculate the angle of incidence (theta t) at which this occurs.

So i have water on the top with refractive index of 1.33, below this i have glass with a refractive index of 1.52, and below that air with a refractive index of 1.00. The phenomenon that causes this to happen is called total internal reflection, i've already figured that bit out. I also have the critical angle of 38.1 degrees, so in the second medium, glass, the beam of light is at an angle of 38.1 degrees to the normal. I need to find the angle of incidence that the light beam is when it's going through the water.
Any help would be appreciated.

Answer 1

You've done the hard part, the rest is just Snell's law at the interface between the water and the glass.

n(water) * sin theta(water) = n(glass) * sin theta(glass)

You know the refractive indices n for the water and glass and theta in the glass, so you can calculate theta(water).