Radar and microwave ovens have a vacuum tube {magnetron} in a magnetic field. Magnetic field rotates electron flow from hot cathode to anode. Rotation makes electron spokes that alternate on and off, at 2.45 gigahertz for microwave ovens, and resonate with an antenna that radiates microwaves.
Ovens {microwave oven}| can use very-high-frequency radio waves {radar wave}, from a magnetron, which heat food as water absorbs radiation. Radar waves reflect from metal, so oven stays cool. Paper and glass do not absorb radar waves much, so they stay cool. Food cooks evenly.
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Date Modified: 2022.0225