while the US government is kind enough to call me an engineer (Sr. Network Engineer) i learned most of my math and physics as general reading--
so waves start out big-- (low frequency sound-- that we can't hear-- then move on to audible waves-- higher frequency is is radio-- and at the far, far far away end of the spectrum is light (Einstein's unified theory? is light a wave or a particle-- and (don't let the smoke bother you-- i am firing up my steam powered brain here--) since a dopple effect it to more something into a higher frequency, and when you travel close to the speed of light, every thing get Red shifted-- I'd say, ultra violet is a lower frequency than infra red-- where light is moving past the visible sprectum.. and can only be "seen" as heat.
So since we don't know yet if light is a extremely high ( or micro nano? wave) wave... or if its particles.. An infra red oven would be totally different technology than Micro waves-- but 500 MHZ sound about right for microwave oven range--
Lots of places still use infra red lights to keep food warm, and the new GE advantix oven combines infra red (for one sourse of heat), with microwaves-- so on some level they are different...
and why DC tech for 5 to 10 Mhz range? (from low voltage systems?) I worked with everything from 5vDC to 3000vDC-- (you really want to be carefull with 3000 vDC! but it looks so pretty! the wires glow almost ulta violet with a corona...)