Dual nature of electron spectrum

[astro2cosmos]

cause of spectra is transition of electron form one state to another state.
but which one? emission spectra or absorption spectra.
or in what case both spectra can be seen?

 

[Bob S]

You can directly excite the 1s -> 3p transition absorption line in a hydrogen atom, but only about 88% of the excited states will go back to the 1s directly by a 3p -> 1s transition.. The other 12% will go back down via the 2s state. Is this your question?
Bob S

 

[astro2cosmos]

You can directly excite the 1s -> 3p transition absorption line in a hydrogen atom, but only about 88% of the excited states will go back to the 1s directly by a 3p -> 1s transition.. The other 12% will go back down via the 2s state. Is this your question?
Bob S

is this transition emit both emission & absorption spectra?

 

[Bob S]

is this transition emit both emission & absorption spectra?

Some gases can absorb their own emission lines. The strong yellow sodium D lines at 5890 Angstroms (two lines separated by about 5 Angstroms) in sodium arc lamps have absorption notches in the center of each broad line, because the cooler gas surrounding the arc is absorbing the emission from the hot arc. This can be seen with a good diffraction grating. [Actually, the emission line width is due in part to collisional broadening.]
Bob S