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I Microwave Heating -- 2.4GHz in, IR radiation out...

  1. Mar 11, 2016 #1
    Microwave oven operates at 2.4 GHz. Consider the situation of making tea or coffee in Microwave where water is heated to 100C to boil.

    Looking at Planck's law / Wien's law, 100C (373K) corresponds to a peak wavelength of 7.8nm or 38.6THz which is in Mid Infrared.

    Effectively materials absorb microwave photons and re emit 15000 times more energetic IR photons.

    How is this taking place? Is it similar to Anti Stokes shift, Raman Effect etc. where photon upshifting could take place.

    Thanks and Regards

  2. jcsd
  3. Mar 11, 2016 #2


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    Staff: Mentor

    No, you couldn't have such a process involving so many photons.

    I wouldn't even talk about microwave photons, as the process is not resonant. It is more a classical EM wave that transfers energy to the water molecules which heat up (radiation energy is converted into rotational, vibrational, and translational motion) and that thermal energy is then re-radiated as IR.
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