Refraction
The deviation from linearity of a beam of light at the interface of two different transparent non-absorbing materials.
Refractive index
The refractive index of a medium nr, is defined by:
where c' is the speed of the
light in the medium and c the speed of the light in a vacuum.
The deviation of the light at the
time of its passage between two mediums is determined by the difference in
their refractive indices.