## Ray Refraction: Finding the depth of a pool

1. The problem statement, all variables and given/known data
A 4.0m wide swimming pool is filled to the top. The bottom of the pool becomes completely
shaded in the afternoon when the sun is 20 degrees above the horizon. How deep is the pool?

2. Relevant equations
$$\theta$$ = arcsin(n2/n1)
n1sin$$\theta$$1= n2sin$$\theta$$2

3. The attempt at a solution
The main thing that I don't understand about this problem is that if the bottom of the pool
is shaded then that means light is not reaching the bottom right? I have only seen problems where something under the surface emitting light has total internal reflection.
Could somebody please explain this to me.