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-   -   microwave oven tuned to resonant frequency of water (https://boards.straightdope.com/sdmb/showthread.php?t=251141)

 lektrikpuke 04-15-2004 02:05 PM

microwave oven tuned to resonant frequency of water

I always thought that microwave ovens were tuned to the resonant frequency of water, but I read that this is not correct on Howstuffworks.com. I asked for an explanation, then, as plates or other articles in the oven supposedly don't get hot (directly) as a result of the microwaves (but indirectly through contact with the heated food). :)

 zimaane 04-15-2004 02:59 PM

My rather limted understanding is that microwave work because water is a polar molecule - the two hydrogen atoms tend to clump together. Since the hydrogens share their electron with the oxygen, the hydrogen end is positive. A microwave works by generating an electromagnetic field within the oven that switches orientation very rapidly - 2400 kHz, or whatever frequency of a micro is. So the water molecules get twisted to and fro very rapidly and heat is generated as a consequence. As a consequnce, a microwave doesn't need any particular frequency, as long as it's fast. My guess would be that the frequency was chosen so as not to interfere with electronic devices, although it didn't work with my cordless phone and microwave.

It's unclear what your question is.

The frequency of a typical microwave has a wavelength of almost five inches, much too big too big to be the resonant frequency of a water molecule which is around the visible spectrum.

 Q.E.D. 04-15-2004 03:30 PM

Quote:
 Originally Posted by lektrikpuke I always thought that microwave ovens were tuned to the resonant frequency of water, but I read that this is not correct on Howstuffworks.com.
No, microwave ovens are not tuned to any particular resonance of water. I did a Staff Report that touches on this subject. The upshot is that if the oven were tuned thusly, the absorption of microwave energy would be so great as to prevent the interior of most foods from cooking at all.

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