The ratio of speed of light in air to that of a material is a coefficient in the trigonometric law of Snellius and is known as the "index" of this process.
The square of a constant related to this phenomenon is equal to the product of the permeability and permittivity of a medium. A form of this phenomenon occurring in an anisotropic medium is known as the "double" variety, or birefringence, whereas total internal reflection is actually another type of this. The ratio of speed of light in air to that of a material is a coefficient in the trigonometric law of Snellius and is known as the "index" of this process. FTP, name this "bending" of light rays when changing media.
The square of a constant related to this phenomenon is equal to the product of the permeability and permittivity of a medium.
{Refraction}