Spectroscopy studies the emission or absorption of electromagnetic radiation by matter. Spectroscopy also studies the scattering of light and the rotation of the plane of polarization produced by optically active substances.
The series of frequencies absorbed by a sample is called an absorption spectrum. The series of frequencies emitted by a sample is called the emission spectrum. Spectra can also be classified into:
- Line spectra are made up of discrete frequencies that appear in the form of bands. These spectra are obtained by heating a gas that is not at very high pressure.
- Continuous spectra are formed by a continuous range of frequencies. Solids and liquids when heated usually give rise to continuous spectra.