The use of light, sound or particle emission to study matter. The emissions are, in many cases, able to provide information about the properties of the matter under investigation.
The device often used for such analysis is a spectrometer, which records the spectrum of light emitted (or absorbed) by a given material, especially in analytical chemistry and physical chemistry fields, where the light can be used to determine the chemical composition of a substance because of signature spectral lines emitted by known elements.