and different parts of the body resonate at different frequencies...part of the reason ~2.4 GHz was picked for the common household microwave is water molecules resonate there (and other harmonically related frequencies too... it's why a lot of the unlicensed ISM stuff is allocated there: crappy atmospheric propagation). also the necessary magnetron and waveguide for that freq is conveniently sized for a kitchen appliance and not too complicated.
EDIT: see proper principle of operation in reply below
and different parts of the body resonate at different frequencies...
part of the reason ~2.4 GHz was picked for the common household microwave is water molecules resonate there(and other harmonically related frequencies too... it's why a lot of the unlicensed ISM stuff is allocated there: crappy atmospheric propagation). also the necessary magnetron and waveguide for that freq is conveniently sized for a kitchen appliance and not too complicated.EDIT: see proper principle of operation in reply below