In order to answer this question, I realized that I needed to know the index
of refraction for ruby, so I went and looked it up. It's 1.762 to 1.770 .
I started trying to remember how to use this number and the critical angle
to find the index of refraction of the other medium. That's when I saw the
absurd unit "degrees celsius" for the critical angle, and I got discouraged.
But I perked up very quickly, when I realized that I'm still on the "index of
refraction" list, and while I'm there, I might as well just go ahead and
look up ethyl alcohol too.
It's 1.36 .
