Emission line.html



It has been suggested that Atomic emission spectrum be merged into this article or section. (Discuss)

An element's emission spectrum is the relative intensity of electromagnetic radiation of each frequency it emits when it is heated (or more generally when it is excited).

When the electrons in the element are excited, the additional energy pushes the electrons to higher energy orbits. When the electrons fall back down and leave the excited state, energy is re-emitted in the form of a photon, the wavelength of the photon being determined by the amount of energy that was necessary to keep that particular electron in its excited state. These emitted photons form the element's emission spectrum.

The emission spectrum can be used to determine the composition of a material, since it is different for each element of the periodic table. One example is identifying the composition of stars by analysing the received light.

An absorption spectrum occurs when light passes through a cold, dilute gas and atoms in the gas absorb at characteristic frequencies; since the re-emitted light is unlikely to be emitted in the same direction as the absorbed photon, this gives rise to dark lines (absence of light) in the spectrum. The light emitted from an excited atom can not be directed toward the observer, so the light appears to be missing from the continuous spectrum.

Emission spectrum of Hydrogen

Emission spectrum of Iron

See also

• Atomic spectral lines
• Molecular radiation
• Rydberg formula
• Astronomical spectroscopy
• Continuous spectrum
• Absorption spectrum
• Emission (electromagnetic radiation)
• Fraunhofer lines

External links

• Emission Spectrum Photos of Various Light Sources
• Color Simulation of Element Emission Spectrum Based on NIST data
• Hydrogen emission spectrum
• Emissions Spectrum Java Applet