What is the relationship between the "critical angle" of a material
and its "refractive index"?

Hi,

Mathematically:

The formula equating the critical angle to n (refractive index) is 
critical angle = sin-1(1 / n). 

http://www.usfacetersguild.org/articles/bob_keller/refractive_index/

*Please go to the above link to see the equation in a clearer
formatted way and also read more on the fundamental concepts of
Refractive Index and Critical Angle relations.


Any clarifications needed? Don't hesitate to ask.
Regards
Landog-ga