Refractive index of glass and its dispersion for visible light

Abstract

The classification of optical glass and empirical relations between the refractive index and its dispersion are discussed in terms of moments of the glass's IR and UV absorption spectra. The observed linear dependence of index on dispersion within glass families is shown to arise primarily from the approximately linear superposition of the electronic absorptions of glass former and glass modifiers. The binary classification into crown and flint glasses is also based primarily on electronic spectra: Crown glasses are "wide-gap" materials with excitation energies greater than ~12.4 eV, while flint glasses are their "narrow-gap" counterpart.