I always wondered about that. I’m an old ham radio operator and I have wondered how the standing waves don’t fry the transmitter in a microwave oven. Is there some weird trick with resonance or something?
That's why you never run it empty. You need something with water in it to absorb the energy.
I was still in school working full time with the guy, did not know enough at the time to ask questions.
He did describe efforts to distribute the energy. But now how.
Said they would cook stuff and look at the pattern of heating.
Not smooth, until Sharp invented the rotating platter.
Someone made a wind up platter as I recall.