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Homework Help: A few questions on blackbody radiation

  1. Jul 12, 2011 #1
    1. The problem statement, all variables and given/known data

    Suppose we have a copper foil at room temperature 300 K°, in the dark.

    If we irradiate it on both sides with laser beams at frequency , say 10^ 13 Hz, one would expect a temp of 500 K° and EMR at 10^ 13.

    Actually it radiates , according Plancks law, at higher frequencies up to visible light
    over 4x 10^ 14 Hz.
    Where does the surplus energy come from?

    What happens when EMR hits the surface?

    please say if these statements are right or wrong:

    1) protons oscillate at 10^13 and pass on oscillation to inner protons
    2) neutrons oscillate but do not emit radiation
    3) electrons jump to outer orbits and fall back realeasing radiation
    4) only the outside one free electron jumps up and down
    5) the other electrons do not absorb energy
    6) the inside free electron flow inside the foil toward cooler atoms

    One would think that, whatever the answer to these and other aspects I ignored and you
    might add, the highest level of energy is 10^ 13

    so WHO is oscillating in visible spectrum, only outer fre electrons?
    and where does the energy come from, certainly not from laser or room!

    II) suppose the volume of foil 1 mm^3
    how do we calc total energy?
    I read Stefan's law says it depends only on Temp^4 is it sigma 6.25x 10^10 ( what? Joules?)
    if volume doubles, what happens?
    Last edited: Jul 12, 2011
  2. jcsd
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