If D is below zero, the medium is claimed to have optimistic dispersion or typical dispersion. If D is greater than zero, the medium has unfavorable dispersion. If a light pulse is propagated via a Generally dispersive medium, the result is the higher frequency factors decelerate over the decrease frequency https://tysonqkiea.eedblog.com/29965654/sound-system-things-to-know-before-you-buy