Emission spectrum

An emission spectrum is the distribution of wavelengths or frequencies emitted by a substance or source. Its features reflect the emitting material, physical conditions, and processes producing the radiation.

Atomic emission: Radiation produced when excited atoms release energy as electrons move to lower energy states. Its discrete transitions produce the characteristic lines seen in many emission spectra.
Electromagnetic spectrum: The full range of electromagnetic radiation, organized by frequency or wavelength. An emission spectrum occupies a portion of this broader range.
Spectroscopy: The study of interactions between matter and electromagnetic radiation as a function of wavelength or frequency. It uses emission spectra to analyze substances and physical processes.
Absorption spectrum: The distribution of wavelengths or frequencies absorbed by a substance from incident radiation. Its dark features mark radiation removed, unlike emission features that mark radiation produced.
Spectral line: A narrow wavelength or frequency feature in a spectrum, associated with a specific radiative transition or resonance. Individual lines mark particular transitions within an emission spectrum.
Photon: A quantum of electromagnetic radiation carrying energy and momentum. Emission processes produce photons whose energies determine spectral positions.
Flame test: A qualitative chemical test that identifies some elements by the characteristic colors they produce in a flame. Flame colors arise from element-specific emission lines.
Scattering spectrum: The wavelength distribution of radiation redirected or frequency-shifted by interactions with matter. Scattering redistributes incident light rather than requiring the source to create the measured photons.
Black-body radiation: Electromagnetic radiation whose spectrum depends only on a body's temperature when it absorbs and emits perfectly. Hot, dense sources can produce a continuous emission spectrum approximating this distribution.
Wavelength: The spatial period of a wave, measured between successive points in the same phase. Emission spectra are commonly plotted as intensity against wavelength.

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