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Why can't you put metal in a microwave? - Aaron Slepkov

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TEDEd Animation

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In 1945, engineer Percy Spencer was standing near a RADAR device that produced high-intensity microwaves and noticed that his candy bar had melted. He then exposed popcorn kernels to the magnetron device, and sure enough, they popped. Soon after, the first microwave oven became available, using the very same technology. So, how does it work? Aaron Slepkov explores the science of microwave ovens.

Additional Resources for you to Explore

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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TED-Ed Animations feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

Meet The Creators

  • Educator Aaron Slepkov
  • Director Yuriy Polyashko, Darvideo Animation Studio
  • Narrator Jack Cutmore-Scott
  • Storyboard Artist Nikita Bondarenko, Dmytro Novitskyi
  • Animator Ann Homenyuk
  • Art Director Orest Smilyanets
  • Sound Designer Stepan Vasylchenko
  • Music Reality Check
  • Director of Production Gerta Xhelo
  • Produced by Abdallah Ewis, Anna Bechtol
  • Editorial Director Alex Rosenthal
  • Editorial Producer Cella Wright
  • Fact-Checker Charles Wallace

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