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Electromagnetic wave propagation/dissipation

  1. Nov 22, 2012 #1
    Hey all,

    just wondering over a very naive question but I couldn't really find the answer by looking through the web. So electromagnetic waves are self sustaining and they don't lose energy while traveling through space, except if the photons they're made out of do "collide" with matter which doesn't give off radiation at the same frequency and wavelength and the original photon's energy gets transformed into heat/kinetic energy. So what would happen if you would operate a microwave oven with the door open and stand right next to it? (asuuming that was possible) Would you heat up as well? Or would the waves/photons just be absorbed by air molecules and heat them up before they reach you? Sounds stupid but I was very interested in that ^^

    And furthermore, if I may add this related question: How come then that radio/television waves are transmitted over such a large distance without first being absorbed. Something to do with the longer wavelength?

    thx very much
     
  2. jcsd
  3. Nov 22, 2012 #2

    Simon Bridge

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    You can get a nasty burn off a microwave oven like that - yes.
    http://en.wikipedia.org/wiki/Microwave_burn

    Note: different substances absorb, scatter, transmit, and reflect EM waves differently - as you will experience by comparing the view through a glass window with that through an oak door. The same substance can have different transparencies to different wavelengths - like water absorbs microwaves from the oven very well - a few centimeters is all it takes, but visible light can penetrate quite a bit further eg. twice the depth of a swimming pool or more.
    Also see:
    http://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water

    These are thinks you could have looked up yourself ... what I want you to take away from these comments is the realization that you can use common everyday experiences to check your ideas about physics questions.
     
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