imported>Qwerfjkl: Added 1 {{Bare URL inline}} tag(s) using a script. For other recently-tagged pages with bare URLs, see :Category:Articles with bare URLs for citations from August 2024

2024-08-28T14:12:31Z

Added 1 {{Bare URL inline}} tag(s) using a script. For other recently-tagged pages with bare URLs, see Category:Articles with bare URLs for citations from August 2024

New page

{{Short description|Type of mirror}}
{{More citations needed|date=September 2022}}
[[File:Specchi.jpg|right|thumb|250px|Example of a second-surface mirror (''left'') and a first-surface mirror (''right''). In both pictures, the pen is touching the surface of the mirror. "Ghosting" (a faint reflection from the first layer) is visible in the left image (more obvious when this file is displayed at full-size).]]
[[File:Six of the 18 James Webb Space Telescope mirror segments.jpg|right|thumb|250px|Technicians assemble 6 of the 18 first-surface mirrors used in the [[James Webb Space Telescope]].]]
A '''first-surface mirror''' or '''front-surface mirror''' (also commonly abbreviated '''FS mirror''' or '''FSM''') is a [[mirror]] with the reflective surface being above a backing, as opposed to the conventional, second-surface mirror with the reflective surface behind a transparent substrate such as [[glass]] or [[Poly(methyl methacrylate)|acrylic]].<ref>{{Cite web |last=Paschotta |first=Dr Rüdiger |title=First Surface Mirrors |url=https://www.rp-photonics.com/first_surface_mirrors.html |access-date=2022-08-30 |website=www.rp-photonics.com |language=en}}</ref>

Historically, the [[bronze mirror]], an FSM type, was standard from ancient times until relatively recent centuries. These were simply highly polished pieces of [[bronze]] or other metals, usually small and round, and designed for a person to see their face.

First-surface mirrors are now made for applications requiring a strict reflection without a ''ghosting'' effect as seen with a second-surface mirror, where a faint secondary reflection could be observed, coming from the front surface of the glass. This includes most optics applications where light is being manipulated in a specific manner. [[Reflecting telescope]]s, [[rear-projection television]]s, [[periscope]]s, [[non-reversing mirror]]s, high-quality [[kaleidoscope]]s, and the animation process.

In cases where the mirror is subjected to extreme cold (as low as 33 K as in the [[James Webb Space Telescope]]), a polished pure [[beryllium]] mirror is used without a first-surface coating in order to eliminate deformations caused by differing coefficients of [[thermal expansion]].

First-surface mirrors are more sensitive than back-surface mirrors and may be damaged by cleaning as the reflective surface is not protected by glass.<ref>http://google.co.uk/books/edition/Optics_for_Engineers/11iz-UKrWf4C?pg=PA43&gbpv=1 {{Bare URL inline|date=August 2024}}</ref>

== Silvering ==
{{main|silvering}}

The "[[silvering]]" on a front-surface mirror is usually [[aluminium]] for [[visible light]] and [[gold]] for [[infrared]] radiation.

==References==
{{reflist}}

[[Category:Mirrors]]

{{optics-stub}}

First-surface mirror - Revision history

imported>Qwerfjkl: Added 1 {{Bare URL inline}} tag(s) using a script. For other recently-tagged pages with bare URLs, see :Category:Articles with bare URLs for citations from August 2024