Your microwave oven works thanks to a particular kind of electromagnetic radiation that excites the water molecules in your food. Microwave ovens typically operate with waves with frequencies of about 2.45 GHz. This is also the frequency used by wifi!
The corresponding wavelength is, considering the speed of light in air:
λ = 299,702,547 m/s / 2.45 × 10⁹ Hz = 12.23 cm
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