In 1621, a Dutch physicist named Willebrord Snell (1591-1626), derived the relationship between the different angles of light as it passes from one transperent medium to another. When light passes from one transparent medium to another, it bends according to Snell’s law which states:
that the angle of refraction is
related to the angle of incidence via
nI sin(θI ) = nR sin(θR )
with nI and nR being the index of refraction for the material on the incident side and
refracted side, respectively.

Below are PDF files containing the refractive index of various substances.

Refraction Index of Various Substances

Refraction Index of Various Substances 2