Index-matching material: Difference between revisions

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In [[optics]], an '''index-matching material''' is a substance, usually a liquid, cement (adhesive), or [[gel]], which has an [[index of refraction]] that closely approximates that of another object (such as a lens, material, fiber-optic, etc.). They are used for various purposes, largely related to reducing the [[Fresnel reflection]] when light hits the surface of the object.

When two substances with the same index are next to each other, light passes from one to the other with neither [[fresnel reflection|reflection]] nor [[refraction]]. As such, they are used for various purposes in science, engineering, and art.

For example, in a popular home experiment, a glass rod is made almost invisible by immersing it in an index-matched transparent fluid such as [[mineral spirits]].<ref>[http://www.optics4kids.org/home/content/classroom-activities/medium/lose-a-glass-in-a-glass/ Optics For Kids - "Lose a glass in a glass" home experiment]</ref>

==In microscopy==

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==In art conservation==

{{seealso|Conservation and restoration of glass objects}}

If a sculpture is broken into several pieces, [[Conservation (cultural heritage)|art conservators]] may reattach the pieces using an adhesive such as [[Paraloid B-72]] or [[epoxy]]. If the sculpture is made of a transparent or semitransparent material (such as glass), the seam where the pieces are attached will usually be much less noticeable if the refractive index of the adhesive matches the refractive index of the surrounding object. Therefore, art conservators may measure the index of objects and then use an index-matched adhesive. Similarly, losses (missing sections) in transparent or semitransparent objects are often filled using an index-matched material.<ref>{{cite journal|title=Controlling the refractive index of epoxy adhesives |authors=John M. Messinger and Peter T. Lansbury |url=http://cool.conservation-us.org/jaic/articles/jaic28-02-006.html |journal=Journal of the American Institute for Conservation |year=1989 |volume=28 |number=2 |pages=127–136}}</ref>

==In optical component adhesives==

Certain optical components, such as a [[Wollaston prism]] or [[Nicol prism]], are made of multiple transparent pieces that are directly attached to each other. The adhesive is usually index-matched to the pieces. AHistorically, common[[Canada index-matchedbalsam]] adhesivewas used in this application, but it is now more common to use [[Canada balsamepoxy]] or other synthetic adhesives.

==References==

*{{FS1037C}}

{{reflist}}

==External links==

* [http://www.optics4kids.org/home/content/classroom-activities/medium/lose-a-glass-in-a-glass/ Home experiment based on index matching between glass and paint thinner]

[[Category:Fiber optics]]