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Heat from radiation, why high v doesn't heat stuff?

  1. Jan 7, 2009 #1
    Why does lower frequency radiation, like infrared, contribute to heating up an object so much more than the higher frequency radiation, like visible light?

    The higher frequency radiation has more energy.

    If you shine a light on something it doesn't get noticeably hotter, but if you put it in the microwave...

    Same with the sun, the visible light is not what causes objects to heat up so much, yet it transfers more energy per unit time.
     
  2. jcsd
  3. Jan 7, 2009 #2

    Astronuc

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    Staff: Mentor

    Glass and water are optically 'transparent' but absorb (or block) in the infrared. That's why cars get hot inside in the sun.

    If you shine an intense light at your hand, I believe you will feel the heat. Remember micrwaves are about 1 kW, but flashlights are a few watts and lightbulbs are one the order of 60 to 150 watts.
     
  4. Jan 8, 2009 #3
    So if I had a 1kw flashlight that radiated only visible light it would be just as good a heater as a 1kw heater that radiated only infrared?
     
  5. Jan 8, 2009 #4

    russ_watters

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    Staff: Mentor

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