Editing Optical spectrometer (section)

==Spectroscopes==
{{Infobox laboratory equipment
|name    = Spectroscope
|image    = Spektrometr.jpg
|alt     = <!-- See Wikipedia:Alternative text for images -->
|caption   =
|acronym   =
|other_names = Spectrograph
|uses    =
|related   = [[Mass spectrograph]]
}}
[[Image:Optical spectrometers.png|thumb|right|Comparison of different diffraction based spectrometers: Reflection optics, refraction optics, fiber/integrated optics {{Citation needed|date=October 2013}}]]
Spectroscopes are often used in [[astronomy]] and some branches of [[chemistry]]. Early spectroscopes were simply [[Triangular prism (optics)|prisms]] with graduations marking wavelengths of light. Modern spectroscopes generally use a [[diffraction grating]], a movable [[Diffraction#Single-slit diffraction|slit]], and some kind of [[photodetector]], all automated and controlled by a [[computer]]. Recent advances have seen increasing reliance of computational algorithms in a range of miniaturised spectrometers without diffraction gratings, for example, through the use of quantum dot-based filter arrays on to a CCD chip<ref>{{Cite journal|last1=Bao|first1=Jie|last2=Bawendi|first2=Moungi G.|date=2015-07-01|title=A colloidal quantum dot spectrometer|url=https://www.nature.com/articles/nature14576|journal=Nature|language=en|volume=523|issue=7558|pages=67–70|doi=10.1038/nature14576|pmid=26135449|bibcode=2015Natur.523...67B|s2cid=4457991|issn=1476-4687}}</ref> or a series of photodetectors realised on a single nanostructure.<ref>{{Cite journal|last1=Yang|first1=Zongyin|last2=Albrow-Owen|first2=Tom|last3=Cui|first3=Hanxiao|last4=Alexander-Webber|first4=Jack|last5=Gu|first5=Fuxing|last6=Wang|first6=Xiaomu|last7=Wu|first7=Tien-Chun|last8=Zhuge|first8=Minghua|last9=Williams|first9=Calum|last10=Wang|first10=Pan|last11=Zayats|first11=Anatoly V.|date=2019-09-06|title=Single-nanowire spectrometers|journal=Science|volume=365|issue=6457|pages=1017–1020|doi=10.1126/science.aax8814|pmid=31488686|bibcode=2019Sci...365.1017Y|s2cid=201845940|doi-access=free}}</ref>

[[Joseph von Fraunhofer]] developed the first modern spectroscope by combining a prism, diffraction slit and [[refracting telescope|telescope]] in a manner that increased the spectral resolution and was reproducible in other laboratories. Fraunhofer also went on to invent the first diffraction spectroscope.<ref name="Brand 37">{{cite book |title=Lines of Light: The Sources of Dispersive Spectroscopy, 1800–1930 |last=Brand |first=John C. D. |publisher=Gordon and Breach Publishers |year=1995 |isbn=978-2884491624 |pages=37–42 }}</ref> [[Gustav Robert Kirchhoff]] and [[Robert Bunsen]] discovered the application of spectroscopes to chemical analysis and used this approach to discover [[caesium]] and [[rubidium]].<ref>{{cite journal|title=The discovery of the elements. XIII. Some spectroscopic discoveries|pages=1413–1434|last=Weeks|first=Mary Elvira|author-link=Mary Elvira Weeks|doi=10.1021/ed009p1413|journal=[[Journal of Chemical Education]]|volume=9|issue=8|year=1932|bibcode=1932JChEd...9.1413W}}</ref><ref>{{cite web|title=Robert Bunsen|url=http://www.infoplease.com/biography/var/robertbunsen.html|work=infoplease|publisher=[[Pearson Education]]|year=2007|access-date=2011-11-21}}</ref> Kirchhoff and Bunsen's analysis also enabled a chemical explanation of [[Astronomical spectroscopy#Stars and their properties|stellar spectra]], including [[Fraunhofer lines]].<ref name="Brand 63">{{harvnb|Brand|1995|p=63}}</ref>

When a material is heated to [[incandescence]] it emits [[light]] that is characteristic of the atomic makeup of the material.
Particular light frequencies give rise to sharply defined bands on the scale which can be thought of as fingerprints. For example, the element [[sodium]] has a very characteristic double yellow band known as the Sodium D-lines at 588.9950 and 589.5924 nanometers, the color of which will be familiar to anyone who has seen a low pressure [[sodium vapor lamp]].

In the original spectroscope design in the early 19th century, light entered a slit and a [[collimating lens]] transformed the light into a thin beam of parallel rays. The light then passed through a prism (in hand-held spectroscopes, usually an [[Amici prism]]) that [[refraction|refracted]] the beam into a spectrum because different wavelengths were refracted different amounts due to [[dispersion (optics)|dispersion]]. This image was then viewed through a tube with a scale that was transposed upon the spectral image, enabling its direct measurement.

With the development of [[photographic film]], the more accurate [[#Spectrographs|spectrograph]] was created. It was based on the same principle as the spectroscope, but it had a camera in place of the viewing tube. In recent years, the electronic circuits built around the [[photomultiplier]] tube have replaced the camera, allowing real-time spectrographic analysis with far greater accuracy. Arrays of photosensors are also used in place of film in spectrographic systems. Such spectral analysis, or spectroscopy, has become an important scientific tool for analyzing the composition of unknown material and for studying astronomical phenomena and testing astronomical theories.

In modern spectrographs in the UV, visible, and near-IR spectral ranges, the spectrum is generally given in the form of photon number per unit wavelength (nm or μm), wavenumber (μm<sup>−1</sup>, cm<sup>−1</sup>), frequency (THz), or energy (eV), with the units indicated by the [[abscissa]]. In the mid- to far-IR, spectra are typically expressed in units of Watts per unit wavelength (μm) or wavenumber (cm<sup>−1</sup>). In many cases, the spectrum is displayed with the units left implied (such as "digital counts" per spectral channel).

[[Image:Units visible spectrum.png|thumbnail|left|550px|A comparison of the four abscissa types typically used for visible spectrometers.]]
[[Image:Units IR spectrum.png|thumb|left|550px|A comparison of the four abscissa types typically used for infrared spectrometers.]]

=== In Gemology ===
[[Gemology|Gemologists]] frequently use spectroscopes to determine the absorption spectra of gemstones, thereby allowing them to make inferences about what kind of gem they are examining.<ref>{{Cite web|title=Spectroscope - The Gemology Project|url=http://gemologyproject.com/wiki/index.php?title=Spectroscope#Use_of_the_spectroscope|access-date=2022-01-04|website=gemologyproject.com}}</ref> A gemologist may compare the absorption spectrum they observe with a catalogue of spectra for various gems to help narrow down the exact identity of the gem.{{clear}}