In this lesson we learned that microwave light with a frequency of 2.5 GHz heats water very efficiently. In practice, slightly higher microwave frequencies (than 2.5 GHz) are considerably more ‘resonant’ with the dipolar water molecule. You can dig deeper and learn how the microwave oven is designed to be less efficient in order to be more useful by consulting this answer on Quora “Why aren’t microwaves tuned to the resonant frequency of water? What would happen if they were?”

Did you know that a pair of grapes will spark in a microwave oven, forming a kind of “ball lightning”? Mysteriously, a single whole grape never sparks. Why? Metals and other conductors can spark in the microwave oven. Does this mean that grapes act as conducting objects? Recent research suggests that no, grapes are not metallic balls, but are, rather, perfectly-sized transparent microwave resonators. Read all about it here, or check out this informative Veritasium video.

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