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Quick question about Microwave radiation

  1. May 8, 2010 #1
    I read in a book that:

    Microwaves are considered lower in energy than infrared waves because they do not affect all molecules, only the polar ones. Polar molecules have slightly different electrical charges at their opposite ends, making them more responsive to microwave radiation than nonpolar molecules. Infrared heat, on the other hand, increases the vibration of nearly all molecules.​

    Isn't it true that Microwaves are higher in energy than infrared waves because they contain shorter wavelengths? Isn't it true that compared to Infrared radiation, Visible light radiation, UV-Rays, Microwaves, X-Rays, and Gamma rays are all more energetic?

    Why do microwaves, according to this book, only affect polar molecules?

    If anyone can provide for me an explanation that can be applied universally, I would be grateful.

    Thanks in advance!
  2. jcsd
  3. May 8, 2010 #2


    User Avatar

    Staff: Mentor

    No, microwaves have longer wavelengths than infrared. Microwaves fall between infrared and radio in the electromagnetic spectrum.

    Electromagnetic spectrum diagram
  4. May 8, 2010 #3
    Gross. I thought microwaves were higher in energy than visible light. For years.
    Bit of a Miss Teen USA South Carolina moment...
  5. May 15, 2010 #4
    Microwaves are far lower in frequency than infrared - therefore, they also have longer wavelengths.
    As to the effect upon polar molecules, that is only one mechanism of energy transfer; others only occur at interfaces or in vacuum, and lots of other ways. The polar molecule coupling mechanism is very important at the frequency of microwave ovens: 2,450 Megahertz (12.2 cm wavelength). However, there is another important mechanism for heat generation that relies upon ionic species, for example the sodium and chloride ions from salt. Here, the energy stored in the microwaves is transferred kinetically by accelerating the ions and causing collisions with unionized species, such as water, and that results in heat.
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