A microwave oven is a kitchen appliance that uses microwave radiation to heat and cook food. Microwaves are a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter. In microwave ovens, the waves primarily cause water molecules in the food to vibrate, generating heat through a process known as dielectric heating. This heat cooks the food quickly and efficiently.
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How Microwaves Work by National MagLab (2017)
Source. A bit meh. Does not mention the word cavity magnetron!How a Microwave Oven Works by EngineerGuy
. Source. Cool demonstration of the standing waves in the cavity with cheese!