Editing Mirror (section)

==Types of mirrors==
[[File:UniversumUNAM27.JPG|thumb|A curved mirror at the [[Universum (UNAM)|Universum museum]] in Mexico City. The image splits between the convex and concave curves.]]
[[File:Mirror statue - Győr, 2015.10.31.JPG|thumb|A large convex mirror. Distortions in the image increase with the viewing distance.]]
Mirrors can be classified in many ways; including by shape, support, reflective materials, manufacturing methods, and intended application.

===By shape===
Typical mirror shapes are [[plane mirror|planar]] and [[Curved mirror|curved]] mirrors.

The surface of curved mirrors is often a part of a [[sphere]]. Mirrors that are meant to precisely concentrate parallel rays of light into a point are usually made in the shape of a [[paraboloid of revolution]] instead; they are used in telescopes (from radio waves to X-rays), in antennas to communicate with [[broadcast satellite]]s, and in [[solar furnace]]s. A [[segmented mirror]], consisting of multiple flat or curved mirrors, properly placed and oriented, may be used instead.

Mirrors that are intended to concentrate sunlight onto a long pipe may be a [[circular cylinder]] or of a [[parabolic cylinder]].<ref>{{cite web |title=Linear Concentrator System Concentrating Solar-Thermal Power Basics |url=https://www.energy.gov/eere/solar/linear-concentrator-system-concentrating-solar-thermal-power-basics |website=Office of Energy Efficiency & Renewable Energy |publisher=US Dept. Of Energy |access-date=23 January 2023 |archive-date=23 January 2023 |archive-url=https://web.archive.org/web/20230123062745/https://www.energy.gov/eere/solar/linear-concentrator-system-concentrating-solar-thermal-power-basics |url-status=live }}</ref>

===By structural material===
The most common structural material for mirrors is glass, due to its transparency, ease of fabrication, rigidity, hardness, and ability to take a smooth finish.

====Back-silvered mirrors====
The most common mirrors consist of a plate of transparent glass, with a thin reflective layer on the back (the side opposite to the incident and reflected light) backed by a coating that protects that layer against abrasion, tarnishing, and [[corrosion]]. The glass is usually soda-lime glass, but lead glass may be used for decorative effects, and other transparent materials may be used for specific applications.<ref>{{Cite web |last=Lowder |first=Stephanie |date=2015-01-23 |title=The History of Mirror: Through A Glass, Darkly |url=https://www.furniturelibrary.com/mirror-glass-darkly/ |access-date=2025-04-24 |website=Bienenstock Furniture Library |language=en-US}}</ref>

A plate of transparent [[plastic]] may be used instead of glass, for lighter weight or impact resistance. Alternatively, a flexible transparent plastic film may be bonded to the front and/or back surface of the mirror, to prevent injuries in case the mirror is broken. Lettering or decorative designs may be printed on the front face of the glass, or formed on the reflective layer. The front surface may have an [[anti-reflection coating]].<ref>{{Cite journal |last=Yamada |first=Y. |last2=Kitamura |first2=S. |last3=Miura |first3=M. |last4=Yoshimura |first4=K. |date=2015-10-01 |title=Improving the optical properties of switchable mirrors based on Mg–Y alloy using antireflection coatings |url=https://linkinghub.elsevier.com/retrieve/pii/S0927024815002755 |journal=Solar Energy Materials and Solar Cells |volume=141 |pages=337–340 |doi=10.1016/j.solmat.2015.06.006 |issn=0927-0248}}</ref>

====Front-silvered mirrors====
Mirrors which are reflective on the front surface (the same side of the incident and reflected light) may be made of any rigid material.<ref name=scha2011/> The supporting material does not necessarily need to be transparent, but telescope mirrors often use glass anyway. Often a protective transparent coating is added on top of the reflecting layer, to protect it against abrasion, tarnishing, and corrosion, or to absorb certain wavelengths.<ref>{{cite journal |last1=Bulkin |first1=Pavel |last2=Gaiaschi |first2=Sofia |last3=Chapon |first3=Patrick |last4=Daineka |first4=Dmitri |last5=Kundikova |first5=Natalya |title=Protective coatings for front surface silver mirrors by atomic layer deposition |url=https://opg.optica.org/oe/fulltext.cfm?uri=oe-28-11-15753&id=431675 |journal=Optics Express |year=2020 |volume=28 |issue=11 |pages=15753–15760 |publisher=Optica Publishing Group |doi=10.1364/OE.388546 |pmid=32549412 |arxiv=1912.01000 |bibcode=2020OExpr..2815753B |s2cid=208526874 |access-date=23 January 2023}}</ref>

====Flexible mirrors====
Thin flexible plastic mirrors are sometimes used for safety, since they cannot shatter or produce sharp flakes. Their flatness is achieved by stretching them on a rigid frame. These usually consist of a layer of evaporated aluminium between two thin layers of transparent plastic.<ref>{{Cite journal |last=Arias |first=Nathaly |last2=Jaramillo |first2=Franklin |date=2020-03-01 |title=Highly reflective aluminum films on polycarbonate substrates by physical vapor deposition |url=https://linkinghub.elsevier.com/retrieve/pii/S0169433219334129 |journal=Applied Surface Science |volume=505 |pages=144596 |doi=10.1016/j.apsusc.2019.144596 |issn=0169-4332}}</ref><ref>{{Cite journal |last=Azzam |first=Yosry A. |last2=Abd El Hameed |first2=Afaf M. |last3=El-Tokhy |first3=Fatma S. |last4=Ismail |first4=Mohamed |last5=El_harony |first5=M. |last6=Sharaf |first6=S. M. |date=2015-01-22 |title=Investigation and treatment of the aluminizing process for mirrors of astronomical telescopes and optical instruments of space vehicles |url=https://linkinghub.elsevier.com/retrieve/pii/S1359431114008862 |journal=Applied Thermal Engineering |volume=75 |pages=856–866 |doi=10.1016/j.applthermaleng.2014.10.015 |issn=1359-4311}}</ref>

===By reflective material===
[[File:Dielectric mirror diagram.svg|thumb|A dielectric mirror-stack works on the principle of [[thin-film interference]]. Each layer has a different [[refractive index]], allowing each interface to produce a small amount of reflection. When the thickness of the layers is proportional to the chosen wavelength, the multiple reflections [[constructive interference|constructively interfere]]. Stacks may consist of a few to hundreds of individual coats.]]
[[File:Hot mirror for a camera.jpg|thumb|A hot mirror used in a camera to reduce red eye]]

In common mirrors, the reflective layer is usually some metal like silver, tin, [[nickel]], or [[chromium]], deposited by a wet process; or aluminium,<ref name=mlink2014/><ref name=saun2004/> deposited by sputtering or evaporation in vacuum. The reflective layer may also be made of one or more layers of transparent materials with suitable [[index of refraction|indices of refraction]].

The structural material may be a metal, in which case the reflecting layer may be just the surface of the same. Metal concave dishes are often used to reflect infrared light (such as in [[space heater]]s) or [[microwave]]s (as in satellite TV antennas). [[Liquid-mirror telescope|Liquid metal telescopes]] use a surface of liquid metal such as mercury.

Mirrors that reflect only part of the light, while transmitting some of the rest, can be made with very thin metal layers or suitable combinations of dielectric layers. They are typically used as [[beamsplitter]]s. A [[dichroic mirror]], in particular, has surface that reflects certain wavelengths of light, while letting other wavelengths pass through. A [[cold mirror]] is a dichroic mirror that efficiently reflects the entire [[visible light spectrum]] while transmitting [[infrared]] wavelengths. A [[hot mirror]] is the opposite: it reflects infrared light while transmitting visible light. Dichroic mirrors are often used as filters to remove undesired components of the light in cameras and measuring instruments.

In [[X-ray optics|X-ray telescopes]], the [[X-ray]]s reflect off a highly precise metal surface at almost grazing angles, and only a small fraction of the rays are reflected.<ref name=pro00/> In [[flying relativistic mirrors]] conceived for [[X-ray laser]]s, the reflecting surface is a spherical [[shockwave]] (wake wave) created in a low-density [[plasma (physics)|plasma]] by a very intense laser-pulse, and moving at an extremely high velocity.<ref name=lewis2008/>

====Nonlinear optical mirrors====
A [[nonlinear optics#Optical phase conjugation|phase-conjugating mirror]] uses [[nonlinear optics]] to reverse the phase difference between incident beams. Such mirrors may be used, for example, for coherent beam combination. The useful applications are self-guiding of laser beams and correction of atmospheric distortions in imaging systems.<ref name=okul1980/><ref name=okul2014/><ref name=boyd1997/>