- another name for double refraction
- The resolution or splitting of a light wave into two unequally reflected waves by an optically anisotropic medium such as calcite or quartz.
- The property or capacity of splitting a beam of light into two beams, each refracted at a different angle, and each polarized at a right angle to the other. Certain crystals such as calcite and quartz have this property.
- The difference in the index of refraction between two beams passing through a substance that has this property. See also refraction index of refraction.