dispersive power

noun Optics.
  1. a measure of the ability of a substance to disperse light, equal to the quotient of the difference in refractive indices of the substance for two representative wavelengths divided by the difference of the refractive index for an intermediate wavelength and 1.
Compare Abbe number.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018