Electromagnetic spectrum

Spectra of objects

Nearly all objects in the universe emit, reflect and/or transmit some light. The distribution of this light along the electromagnetic spectrum (called the spectrum of the object) is determined by the object's composition. Several types of spectra can be distinguished depending upon the nature of the radiation coming from an object:

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• If the spectrum is composed primarily of thermal radiation emitted by the object itself, an emission spectrum occurs.
• Some bodies emit light more or less according to the blackbody spectrum.
• If the spectrum is composed of background light, parts of which the object transmits and parts of which it absorbs, an absorption spectrum occurs.

Electromagnetic spectroscopy is the branch of physics that deals with the characterization of matter by its spectra.

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