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Homework Help: Radiative Transfer + Emissivity

  1. Mar 31, 2010 #1
    1. The problem statement, all variables and given/known data

    This isn't so much of a homework but rather I am trying to understand the physics. The solution to the radiative transfer for a isothermal homogeneous gas of layer consists of one part that describes the absorption and one part that describes the emission.

    My questions about this:

    1. What happens to the light scattered? Does this count here?
    2. What is emissivity - is this emission?
    3. Is light absorbed while it passes throu the gas - does the first term account for this?
    4. Can you use the eq. below to simulate the spectra in which both absorption and emission takes place? I am asking because the in the books I have seen they assume strong emitting gas and takes the first term = 0 and for strong absorbing gas and says that emissivity = source function = 0. You can account for both of them?
    5. What happens if you have different temperatures in the gas? Do you get a mixture of spectra with different temperatures? Is this a troublesome for diagnostics in which temperatures to be determined? Or does the weaker T blend in the the spectra and you only see the spectra of the highest temperature?
    6. What is self-absorption?

    2. Relevant equations

    I (l) = I(0)exp(-kv N l) + Sv(1-exp(-kv N l)

    where Sv is the blackbody, kv absorption coefficient, l is optical length of gas column, N is number of atoms/molecules per volume and I(0) is the intensity before it enters the gas cloud.

    3. The attempt at a solution

    See above.
     
  2. jcsd
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