[zanderbaxa]

Does an atom absorb 100% frequency energy? Does an atom absorb more than one frequency? In emission lines, how can atomic lines be distinguished between to source a and gas cloud the EMW permeated 100 LYs later?

[Unknown008]

Not all atoms absorb 100% energy, because otherwise, you would have seen everything black. Remember that reflection occurs when atoms reject 'excess' energy they have.

Also, atoms tend to released the absorbed energy. For example, the gas cloud would initially absorb, then slowly release the energy in the form of light and heat (sometimes sound too if I'm not mistaken).

And I'm not sure I understand your other question well...

[zanderbaxa]

Do atoms absorb energy from more than one frequency at a time. E.g. An electron (in one orbit) absorbs energy from green light, and another electron absorbs energy from orange?

[TUT317]

Do atoms absorb energy from more than one frequency at a time. E.g. An electron (in one orbit) absorbs energy from green light, and another electron absorbs energy from orange?

Hi Zander,


I think so.

Isn't that how such things as electric lights and television screens work?


Tut

[Unknown008]

Just like anything black can absorb white light. White light is a mixture of every EM frequency from the visible spectrum and no light is given back off. So guess what, the atom got it all! ;)

[ebaines]

Does an atom absorb 100% frequency energy? Does an atom absorb more than one frequency?

I assume we are talking about atomic spectra in this thread - namley emission and absorption lines.

Atoms may "absorb" photons of specific frequencies that correspond to appropriate energy levels that raise the atom's electron from one shell level to another. It takes a very specific wavelenth of light to do this, depending on the particular atom that is being radiated. So no - not 100% of all wavelengths are absorbed by any atom. Then the atom almost immediately re-readiates a photon of the same wavelength as the electron falls back to the lower energy level. The effect that we see is that low density, cool gas clouds tend to obscure radiation from a source behind, and in the spectra we see absorption lines corresponding to the wavelengths of light that the atoms in the gas cloud absorb. Note that when they re-radiate photons they are emitted as light of the same wavelength as was absorbed, but they get radiated out in all directions and hence the light from the source beyond appears darker to the observer in that specific wavelength than it would otherwise.

In emission lines, how can atomic lines be distinguished between to source a and gas cloud the EMW permeated 100 LYs later?

A source of emission (such as a hot dense gas cloud or the corona of a star) will have a spectrum that appears bright in the specific wavelengths that correspond to the electrons' transition from a high energy state to a lower one. The specific wavelengths depend on the constituent atoms of the gas cloud and the energy in it (also on whether there is any shift in the spectra due to the relative motion of the gas cloud and the observer - but that's a different topic). An absorber of emmission (such as a cool low density gas cloud) appears dark in those specific wavelenths. Hence you see spikes in the spectra from the emmission source and dips from the intervening gas cloud.

There's a pretty good article about how this works in this month's edition of "Astronomy" Magazine.

[zanderbaxa]

Your assumption is right.