Why a microwave leaves cold spots: a standing wave 12.2 cm long, and a chocolate bar that measures the speed of light
30seconds
Microwave ovens fill a metal box with radio waves 12.2 cm long. The waves bounce off the walls and add up into a standing wave, a frozen pattern of hot spots and cold spots about 6 cm apart. Food heats where the wave is strong and barely at all where it cancels.
Cook a virtual plate with and without a turntable, then drag a ruler between two hot spots and measure the speed of light the way a bar of chocolate can: spot spacing × 2 × 2.45 GHz.
Deep dive · 5 min
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