Editing Interferometry (section)

====Wavefront splitting inferometers====
A wavefront splitting interferometer divides a light wavefront emerging from a point or a narrow slit (''i.e.'' spatially coherent light) and, after allowing the two parts of the wavefront to travel through different paths, allows them to recombine.<ref name=Verma>{{cite book|last=Verma|first=R.K.|title=Wave Optics|date=2008|publisher=Discovery Publishing House|isbn=978-81-8356-114-3|pages=97–110|url=https://books.google.com/books?id=uuzPcVS_dc0C&pg=PA97}}</ref> Fig.&nbsp;5 illustrates [[Young's interference experiment]] and [[Lloyd's mirror]]. Other examples of wavefront splitting interferometer include the Fresnel biprism, the Billet Bi-Lens, diffraction-grating Michelson interferometer,<ref>{{cite journal | last1=Kolesnichenko |first1=Pavel| last2=Wittenbecher |first2=Lukas| last3=Zigmantas |first3=Donatas |date=2020|title= Fully symmetric dispersionless stable transmission-grating Michelson interferometer |journal = Optics Express| volume= 28|issue=25 |pages=37752–37757| doi = 10.1364/OE.409185 |doi-access=free |pmid=33379604 |bibcode=2020OExpr..2837752K }}</ref> and the [[Rayleigh interferometer]].<ref name=OPI>{{cite web |title=Interferential Devices – Introduction|url=http://www.optique-ingenieur.org/en/courses/OPI_ang_M02_C05/co/Cours_M02C05_1.html |publisher=OPI – Optique pour l'Ingénieur |access-date=1 April 2012}}</ref>

[[File:Young's two-slit experiment and Lloyd's mirror.png|thumb|750px|Figure 5. Two wavefront splitting interferometers]]

In 1803, [[Young's interference experiment]] played a major role in the general acceptance of the wave theory of light. If white light is used in Young's experiment, the result is a white central band of [[constructive interference]] corresponding to equal path length from the two slits, surrounded by a symmetrical pattern of colored fringes of diminishing intensity. In addition to continuous electromagnetic radiation, Young's experiment has been performed with individual photons,<ref>{{cite journal | author-link=Geoffrey Ingram Taylor|first=Sir Geoffrey |last=Ingram Taylor |title=Interference Fringes with Feeble Light| journal = [[Mathematical Proceedings of the Cambridge Philosophical Society]] | volume=15|page=114 |date=1909| url=https://archive.org/details/proceedingsofcam15190810camb/page/114/mode/2up | access-date=7 December 2024}}</ref> with electrons,<ref>{{cite journal | last1 = Jönsson | first1 = C  | date = 1961 | title = Elektroneninterferenzen an mehreren künstlich hergestellten Feinspalten| journal = Zeitschrift für Physik | volume = 161 | issue = 4 | pages = 454–474 | doi = 10.1007/BF01342460 |bibcode = 1961ZPhy..161..454J | s2cid = 121659705 }}</ref><ref>{{cite journal | last1=Jönsson |first1=C |date=1974|title= Electron diffraction at multiple slits |journal = American Journal of Physics| volume= 4|issue=1 |pages=4–11| bibcode = 1974AmJPh..42....4J |doi = 10.1119/1.1987592 }}</ref> and with [[buckyball]] molecules large enough to be seen under an [[electron microscope]].<ref name=Buschhorn2004>{{cite book |title=Fundamental Physics – Heisenberg and Beyond: Werner Heisenberg Centennial Symposium "Developments in Modern Physics" |date=2004 |publisher=Springer |isbn=978-3-540-20201-1 |chapter-url=https://books.google.com/books?id=oLMCFnkFIdoC&pg=PA35|author1=Arndt, M. |author2=Zeilinger, A. |chapter=Heisenberg's Uncertainty and Matter Wave Interferometry with Large Molecules |editor1=Buschhorn, G. W. |editor2=Wess, J.|pages=35–52}}</ref>

[[Lloyd's mirror]] generates interference fringes by combining direct light from a source (blue lines) and light from the source's reflected image (red lines) from a mirror held at grazing incidence. The result is an asymmetrical pattern of fringes. The band of equal path length, nearest the mirror, is dark rather than bright. In 1834, Humphrey Lloyd interpreted this effect as proof that the phase of a front-surface reflected beam is inverted.<ref name=Carroll2010>{{cite web |last=Carroll |first=Brett|title=Simple Lloyd's Mirror |url=http://www.aapt.org/Programs/contests/upload/carroll.pdf|publisher=American Association of Physics Teachers |access-date=5 April 2012}}</ref><ref name=Serway2010>{{cite book|author=Serway, R.A.|author2=Jewett, J.W.|title=Principles of physics: a calculus-based text, Volume 1|date=2010|publisher=Brooks Cole |isbn=978-0-534-49143-7 |pages=905 |url=https://books.google.com/books?id=1DZz341Pp50C&pg=PA904}}</ref>