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Question about the destructive interference of radiation.

  1. May 16, 2012 #1
    If two radiation signals cancel each other out through destructive interference, is it still possible for a material to absorb energy and heat up when exposed to the two radiation signals?
     
  2. jcsd
  3. May 22, 2012 #2
    The thread originator is waiting for a response.
     
  4. May 22, 2012 #3

    Drakkith

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    Staff: Mentor

    The destructive interference merely forces the radiation to be absorbed elsewhere. If your material is larger than the zone of interference the radiation will still be absorbed.
     
  5. May 22, 2012 #4

    Bobbywhy

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    Gold Member

    When identical waves interfere, the amplitude of the resulting wave depends on the relative phase of the two waves. When the peak of one wave aligns with the peak of the second wave, the waves are in phase and produce a wave with the largest possible amplitude. When the peak of one wave aligns with the trough of the other wave the waves are out of phase by and produce a wave with the smallest possible amplitude, zero!
     
  6. May 22, 2012 #5
    The material wont absorb any energy at any spot where the radiation cancels out. If you ever wondered why microwave ovens have either rotating plates or scattering blades, it's because otherwise you would have hot and cold spots in your food where the microwaves add or cancel out.
     
  7. May 23, 2012 #6
    But according to the following statement:

    The energy would still be absorbed. Otherwise if the radiation signals are canceling out and just disappear, that would violate the law of energy conservation because the energy cannot just disappear. Or perhaps, could the interfering signals just pass through the material and continue to travel into space?
     
  8. May 23, 2012 #7
    Note I said hot AND cold spots. The cold spots are where the microwaves interfere destructively. The hot spots are where they interfere constructively.
     
  9. May 24, 2012 #8

    Drakkith

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    Staff: Mentor

    The radiation isn't absorbed at the dark spots where destructive interference happens, but is instead absorbed at the light spots where constructive interference happens.
     
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