A spectrograph.
In the optics, a spectrograph, spectrometer or spectrophotometer is an instrument that splits light into the different colors, just like Newton did with his prism. The resulting measurement of the distribution of light across the different wavelengths is called a spectrum.
The principle by which the spectrograph works is based on the color separation of, for example, a prism or a grating. A quality measure for a spectrograph is the color separating power R = λ / Δλ, where Δλ is the smallest possible wavelength difference in which still separated spectral lines can be observed. Values of 100,000 or more are achievable.
Applications of a spectrograph include, for example, the study of spectral lines of chemicals and in astronomy, where the optical spectrum gives a lot of information about, among other things, the type, velocity and composition of the star.
If the resulting spectrum is recorded, one usually speaks of a spectrograph, and different from a spectroscope or spectrometer. These two terms are often used interchangeably.
The term spectrum comes from the Latin word spectare, which considers, behold, and the like means. It is therefore obvious that the term spectrum was used first for light. Later this concept was extended to all kinds of other vibration phenomena (electrical, acoustic, mechanical, etc.). Instruments that do frequency analyzes in such areas are sometimes also called spectrometers.
In addition, the term spectrometer is commonly used for some instruments that measure a magnitude as a function of another magnitude. One of the best known examples is the mass spectrograph. Also see
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