Question

The critical angle for a light ray travelling from a ruby into ethyl alcohol is 50.6 degrees celsius. Determine the index of refraction for ethyl alcohol.

Answer 1

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  .