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Emission and Absorption bands?

  1. Sep 29, 2009 #1
    I have been wondering lately, as I am quite new to physics.

    If an atom dropped from it's first energy level back to it's ground state, and emitted a photon. Could a photon of the same wavelength excite the atom back to it's first energy level?

    What is the difference between emission and absorption bands?

    Can an atom be excited using the same wavelengths as it's emission bands if they were in order?
  2. jcsd
  3. Sep 29, 2009 #2
    Hello HMS-

    If you have been reading my answers to your previous threads you already know this, but...

    I explained to you the sodium D lines, the 3P to 2P transitions (~5890 and 5895 Angstroms), and the fact that cool sodium atoms surrounding the discharge can absorb some emissions from a hotter sodium atom emitter in a sodium discharge lamp. I specifically mentioned the dark band easily seen in the center of each yellow band using a diffraction grating was the absorption band of the cooler gas. So the hot emission spectrum is much broader than the cool absorption spectrum. Thus the cool gas cannot absorb all the emitted photons from the hot gas.
    Bob S
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