The absorption spectral line or the dark spectral line is a feature of the spectrum , which consists in lowering the radiation intensity near a certain energy.
Absorption lines in electromagnetic spectra are formed when radiation passes through a relatively cold transparent substance. Atoms have the ability to absorb quanta of electromagnetic radiation of strictly defined energies (frequencies), and then re-emit them in an arbitrary direction. As a result, the mass of the substance scatters radiation at certain frequencies, and they do not reach the observer, forming dark (dull) sections in the observed spectrum — lines. By analogy - the spectral line of radiation, where certain frequencies are not scattered, but rather amplified, thereby the detector will emit amplified frequencies.
The spectral lines are very atomically dependent, and can be used to determine the chemical composition of almost any body or material that passes light through itself (gas is usually used). Spectral lines are widely used to determine the chemical composition of stars and other distant objects of space, which cannot be investigated by other methods.
See also
- Spectral line