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A medium is a material. Free space is lack of material, and is not a medium. Check out a good intro physics or electrodynamics text, such a Serway or Griffiths or Jackson if you are unclear. Salsb 15:09, 7 December 2005 (UTC) reply

Am I mistaken, I thought light waves (be they particle or wave) were not the same as electromagnetic radiation? Shouldn't an optical medium be a medium through which light waves travel? maxsch ( talk) 17:48, 6 May 2008 (UTC) reply

never mind, I found the answer in the electromagnetic radiation page. maxsch ( talk) 20:42, 6 May 2008 (UTC) reply