Answer: Absorption lines or Fraunhofer line.
Explanation:
according to experiment carried out by flavour in 1817 acordos lines absorption lines of our fault lines absorption lines refer to the tendency of cool atmospheric gas to absorb the same lines of light. A blackbody object emits radiation of all wavelengths. However, when the radiation passes through a gas, some of the electrons in the atoms and molecules of the gas absorb part of the energy passing through. The particular wavelengths of energy absorbed are unique to the type of atom or molecule. The radiation emerging from the gas cloud will thus be missing those specific wavelengths, producing a spectrum with dark absorption lines.
The atoms or molecules in the gas then re-emit energy at those same wavelengths. If we can observe this re-emitted energy with little or no back lighting (for example, when we look at clouds of gas in the space between the stars), we will see bright emission lines against a dark background. The emission lines are at the exact frequencies of the absorption lines for a given gas. When a continuous spectrum is viewed through some cool gas, dark spectral lines
(called absorption lines) appear in the continuous spectrum.
If the gas is viewed at an angle away from the source of the continuous spectrum, a
pattern of bright spectral lines (called emission lines) is seen against an other-wise
dark background.
