[Speed of RF waves and IR waves is same as 3*10^8 m/s][1]

This seems to be a very elementary question with a straight-forward answer which can be found in every introductory physics text.  I have not, however, been able to find this basic question on PSE with a straight-forward, well-reasoned, not-overly-complicated answer (or any answer for that matter).

Do we want a collection of elementary questions such as this, if they aren't duplicates, even if the answer is easily found in a text?

**Vote up if you think this should be on topic under the new policy, or vote down if you think it should be off topic under the new policy.**

  [1]: http://physics.stackexchange.com/questions/247829/speed-of-rf-waves-and-ir-waves-is-same-as-3-10-8-m-s