; http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr.html

(eq nu (/ c v))

(var nu "index of refraction")
(var c "velocity of light in vacuum")
(var v "velocity of light in the medium")

; Material examples for nu:
;    Vacuum  1.000
;    Air     1.000277
;    Water   4/3
;    Ice     1.31
;    Crown glass 1.50 to 1.62