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Photons emitted by heated objects

  1. Jun 6, 2015 #1
    Hello everyone,

    I have a question. Electrons jumps up the energy level by absorbing a photon and down releasing it, giving off a characteristic spectrum. Then, are the photons released when an object is been heated up due to intermolecular forces, since they are of a full spectrum? Is the kinetic energy of the atoms enough to make the electrons jumps or do they absolutely require a photon?

    Thank you :)
     
  2. jcsd
  3. Jun 6, 2015 #2
    An object at finite temperature emits photons according to Planck's law.
    See https://en.wikipedia.org/wiki/Black-body_radiation.
    If these photons escape the body will cool down to absolute zero unless it is in contact with a heat bath at some temperature. That contact will keep the excited states populated causing the emission, indeed without the need for photons.
     
    Last edited: Jun 6, 2015
  4. Jun 6, 2015 #3

    Janus

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    The photons created from the kinetic energy of the atoms aren't due to electrons changing energy levels, but simply due to the fact that the atoms are vibrating/oscillating. An oscillating charge will emit photons at a frequency equal to that of the oscillation.
     
  5. Jun 6, 2015 #4
    The question was specifically after photons emitted by jumping electrons.
    But yes other degrees of freedom of the object also contribute to the thermal radiation.
    Also the degrees of freedom of a real object do not populate the energy spectrum uniformly.
    This will lead to deviations from Planck's law, which assumes 100% absorption at all wave lengths.
    And then there is still reflection of incident radiation to be considered.
    Further aspects:
    roughness of the surface, which may cause diffuse scattering
    angle dependency of emitted and reflected radiation
    angle dependent polarization
     
    Last edited: Jun 6, 2015
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