Exceeding the speed of light in a particular material

[Loosehead]

I read somewhere months ago that there is a "wave" or something that can travel faster than light in a substance eg water but not faster than c. Does this ring a bell with anyone? Can someone point me at a link? Thanks

[brachiopod]

There was an article in last week's New Scientist about two physicists getting photons to exceed the speed of light.

Excerpt here

[Loosehead]

yeah I read about that. I meant that there is a clear name for some waves/radiation that can exceed the local speed of light. It was demonstrated by using some sort of material that slows light down.

[mjd]

Are you thinking about Cerenkov Radiation see here

http://en.wikipedia.org/wiki/Cherenkov_radiati on

[Loosehead]

Yep that's the stuff, many thanks