Re: Microwave oven
A common misconception. Microwave ovens would work at any practical frequency (wavelength dictates possible oven sizes) given the amount of power used. Water molecule resonance is not required.
I stand corrected.
The only reason they use 2.45GHz is that it's the most suitable of a number of freely usable bands for ISM (Industrial Scientific & Medical) applications with no licence needed.
It's the other way around, 2.45GHz was added to the ISM list because early experiments in microwave cooking used it.