Spectral lines and absorption lines

In summary, the conversation discusses the transparency of the atmosphere and the presence of absorption lines in its composition. While oxygen and nitrogen molecules do not have strong absorption lines in the visible spectrum, they do have weak ones in the electromagnetic spectrum. This explains why the atmosphere appears transparent but still has some absorption of sunlight at certain frequencies.
  • #1
stfaivus
21
3
On PF, to answer why atmosphere is transparent, users explained that atmospheric gases such as oxygen do not have absorption lines in the visible spectrum. On UColorado website, under Spectral Lines, they show that Oxygen has many visible lines in its spectral signature. This confuses me, because I thought absorption lines and an atom's spectral signature lines are the same frequencies, so the information seems to be conflicting.
 
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  • #2
Note that most of the atmosphere is Nitrogen, not Oxygen. Also note that the Nitrogen and Oxygen in the atmosphere are not lone atoms, but diatomic molecules (O2 and N2). Molecule's lines are not the same as its constituent atom's lines. I know this doesn't answer your question, but I would see if you can find O2 and N2's lines.
 
  • #3
If the gases in air, mainly N2 and O2, did not have absorption lines in the visible spectrum, this would solve my question. However on http://en.m.wikipedia.org/wiki/Spectral_line
Spectral lines for air is shown to have many lines in visible light, so I am still not sure...
 
  • #4
Absorption and emission lines are of different intensity. The molecules of the atmosphere do not have first-order absorption lines in the visible range, but do have weak ones, mainly the qxygen and water molecules. So a layer of air even about one metre thick is transparent but the sunlight is a bit absorbed at certain frequencies/wavelength when traversing the whole atmosphere.

ehild
 
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  • #5
does this means that air has strong absorption lines in the electromagnetic spectrum outside of the visible light?
 

1. What are spectral lines?

Spectral lines are narrow bands of light that are emitted or absorbed by atoms or molecules. They are produced when electrons in these particles transition between different energy levels.

2. What is the difference between emission and absorption lines?

Emission lines occur when electrons in an atom or molecule move from a higher energy level to a lower one, releasing energy in the form of light. Absorption lines, on the other hand, occur when electrons absorb energy from incoming light and move to a higher energy level.

3. How are spectral lines used in scientific research?

Spectral lines are used in a variety of scientific fields, including astronomy, chemistry, and physics. They can be used to identify elements and molecules, determine their composition and temperature, and study the properties of stars and galaxies.

4. What causes spectral lines to appear at different wavelengths?

The energy levels of electrons in an atom or molecule are quantized, meaning they can only exist at specific energy levels. When electrons transition between these levels, they emit or absorb light at specific wavelengths, resulting in the appearance of spectral lines at different wavelengths.

5. How do scientists measure spectral lines?

Scientists use spectroscopy, a technique that involves breaking up light into its component wavelengths, to measure spectral lines. This can be done using a spectrometer, which separates light into its wavelengths and measures the intensity of each one, or through other methods such as interferometry and Fourier transform spectroscopy.

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