Correct. The reason why microwaves can cook food isn't the fact that it is a microwave frequency. Microwaves ovens cook by flipping the polarity back and forth. The frequency emitted is the same resonant frequency as water molecules, so the water molecules attempt to align constantly to the ever changing polarity. Movement is heat; thus, the water heats the food.
To set the record straight for the above comment -
- it's true that there isn't a precise frequency needed for microwave ovens to heat food
- however, "polarity flipping" is just a description of electromagnetic radiation itself, and shooting enough EM radiation at food in a frequency range it absorbs will heat it up via dielectric heating
- microwaves have no relationship to any specific resonant frequency of water - the vibration frequencies are orders of magnitude higher https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_... while rotation response inherently does not have a peak
- otherwise, yes, the motion of (polar) molecules induced by an electric field is indeed the mechanism of dielectric heating
