Field of Science

Radar and the chocolate bar

Early in 1940, two British engineers, Harry Boot and John Randall, working under Australian physicist Mark Oliphant built a cavity magnetron, an efficient device for producing high power microwaves as part of an effort to develop better radar detection systems. In this they were eminently successful. By the middle of the year, radar could be used to locate a submarine periscope at six miles. After World War II ended, research on magnetrons continued. In 1946 Percy Spencer, an engineer working at Raytheon, walked through a room in which a magnetron was being tested and noticed that the chocolate bar in his pocket had melted. It occurred to him that the microwaves being generated by the magnetrons could be used to cook food. The next day he placed unpopped popcorn near an operating magnetron, and watched as fluffy white kernels flew around the room. He then tried to cook an egg in the shell, which cooked so quickly it blew up in his colleagues face. Raytheon and Spencer patented the microwave oven in 1950, arguing that it provided a tasty and more sanitary popcorn product. Microwave popcorn is now a ubiquitous part of lab life. In fact, researchers using physical chemistry to develop corn that pops better in the microwave!

Spencer never completed elementary school, but made major contributions to the development of magnetrons for radar and other applications.

Photo of Percy Spencer
Slide show about the microwave patent from PBS History Detectives.

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  1. Worth noting that chocolate melts below body temperature, and, had he realized this at the time, he may not have had the brilliant idea of microwaving popcorn, and I couldn't drive over to walmart and get a $30 korean microwave at 4 in the morning.

  2. True enough, though the melting may have been faster than expected!

  3. Erm, isn't this physics, not chemistry?

    A former physicist

  4. Well...this is technically engineering, I suppose. Microwave work is done by chemists, both spectroscopy and to "cook" reactions, so I would call it fair game. I was lecturing on it the day I posted this...


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