Non-dispersive Media for Light

Are there any other non dispersive media for light besides air/ vacuum. That is, is there any other medium in which all EM radiations will travel with the same velocity?
- Annie (age 18)
NY

I think only a vacuum is a non-dispersive medium. Air doesn't disperse light a lot, because the air is not very dense. However, as you've no doubt noticed, the sky is blue. That means that air does scatter light by a frequency-dependent amount. Basically, any scatterer has some frequency dependence so they're all dispersive.

Mike W.

(published on 03/29/2011)