KnowraRefractive indexLinked fromLinked fromThe 99 pages that link to Refractive index, each with the reason it gives.All 99Broader topic 2Related 88Narrower topic 5Compared with 4Dielectric constantCompared with: For transparent, nonmagnetic materials at optical frequencies, its square approximates relative permittivity.Optical path lengthCompared with: It is a local material property, whereas optical path length accumulates that property along a route.Specific gravityCompared with: It is another material-identification measure, but depends on optical behavior rather than density.Impedance of free spaceCompared with: It changes propagation in matter, where wave impedance generally differs from its vacuum value.