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Could Interference be used to effect one way radiation?

  1. Jul 14, 2012 #1
    If you have radiation from two black body sources at same temperature will they make a maximin minimum Interference pattern that another small black body sphere can be inserted in, in a minimum space. Will they radiate low radiation to the sphere (Due to the radiation energy in that area been low due to Interference) But the radiation to the two sources be a higher energy value?
    Last edited: Jul 14, 2012
  2. jcsd
  3. Jul 14, 2012 #2


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    No, the blackbody radiation from the two sources is not coherent.
  4. Jul 15, 2012 #3
    Just to elaborate somewhat on #2. A black-body emits random phase radiation over a very broad frequency spectrum (Planck spectrum). Interference is entirely absent in any meaningful sense. To quote from the very first part of Wiki article http://en.wikipedia.org/wiki/Black-body_radiation

    "Black-body radiation is the type of electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, or emitted by a black body (an opaque and non-reflective body) held at constant, uniform temperature. The radiation has a specific spectrum and intensity that depends only on the temperature of the body.[1][2][3][4]."

    'thermodynamic equilibrium' is the operative expression here. Any inserted third body feels the same random radiation spectrum regardless of location relative to the other two - if in a uniform temperature environment. Which of course would not apply if the first two black bodies are internally heated to temperatures differering from the external environment. And while emissivity of materials varies widely, precisely the same black-body spectrum is emitted by any material if in temperature equilibrium with it's environment. You will doubtless recall from a posting elsewhere that other considerations may also enter, having nothing to do with interference or surface emissivity phenomena.
  5. Jul 17, 2012 #4
    Thankyou .
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