Editing Interferometry (section)

{{Short description|Measurement method using interference of waves}}
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[[Image:Interferometer.svg|thumb|250px|Figure 1. The light path through a [[Michelson interferometer]]. The two light rays with a common source combine at the half-silvered mirror to reach the detector. They may either interfere constructively (strengthening in intensity) if their light waves arrive in phase, or interfere destructively (weakening in intensity) if they arrive out of phase, depending on the exact distances between the three mirrors.]] 

'''Interferometry''' is a technique which uses the ''[[interference (wave propagation)|interference]]'' of [[Superposition principle|superimposed waves]]  to extract information.<ref>{{cite book |last1 = Bunch |first1 = Bryan H |first2 = Alexander |last2 = Hellemans |title = The History of Science and Technology |publisher = Houghton Mifflin Harcourt |date = April 2004 |page = [https://archive.org/details/isbn_9780618221233/page/695 695] |url = https://archive.org/details/isbn_9780618221233 |url-access = registration |isbn=978-0-618-22123-3}}</ref> Interferometry typically uses [[electromagnetic waves]] and is an important investigative technique in the fields of [[astronomy]], [[Optical fiber|fiber optics]], [[engineering]] [[metrology]], [[optical metrology]], [[oceanography]], [[seismology]], [[spectroscopy]] (and its applications to [[chemistry]]), [[quantum mechanics]], [[Nuclear physics|nuclear]] and [[particle physics]], [[plasma physics]], [[interactome|biomolecular interactions]], surface profiling, [[microfluidics]], mechanical stress/strain measurement, [[velocimetry]], [[optometry]], and making [[hologram]]s.<ref name=HariharanBasics2007>{{cite book|last=Hariharan|first=P.|title=Basics of Interferometry|date=2007|publisher=Elsevier Inc.|isbn=978-0-12-373589-8}}</ref>{{rp|1–2}}

'''Interferometers''' are devices that extract information from interference. They are widely used in science and industry for the measurement of microscopic displacements, [[refractive index]] changes and surface irregularities. In the case with most interferometers, light from a single source is split into two beams that travel in different [[optical path]]s, which are then combined again to produce interference; two [[Incoherent light|incoherent]] sources can also be made to interfere under some circumstances.<ref>{{cite journal|last=Patel|first=R.|author2=Achamfuo-Yeboah, S. |author3=Light R.|author4=Clark M.|title= Widefield two laser interferometry|journal=Optics Express|date=2014|volume=22|issue=22|pages=27094–27101|url=https://www.osapublishing.org/oe/abstract.cfm?uri=oe-22-22-27094|bibcode=2014OExpr..2227094P|doi=10.1364/OE.22.027094|pmid=25401860|doi-access=free}}</ref> The resulting [[interference fringe]]s give information about the difference in [[optical path length]]s. In analytical science, interferometers are used to measure lengths and the shape of optical components with nanometer precision; they are the highest-precision length measuring instruments in existence.  In [[Fourier transform spectroscopy]] they are used to analyze light containing features of absorption or emission associated with a substance or mixture. An [[astronomical interferometer]] consists of two or more separate telescopes that combine their signals, offering a resolution equivalent to that of a telescope of diameter equal to the largest separation between its individual elements.