Prism - Wikipedia
Prism - Wikipedia
Prism - Wikipedia
Prism
In optics, a prism is a transparent optical element with flat, polished surfaces that
refract light. At least two of the flat surfaces must have an angle between them. The
exact angles between the surfaces depend on the application. The traditional
geometrical shape is that of a triangular prism with a triangular base and
rectangular sides, and in colloquial use "prism" usually refers to this type. Some
types of optical prism are not in fact in the shape of geometric prisms. Prisms can
be made from any material that is transparent to the wavelengths for which they
are designed. Typical materials include glass, plastic, and fluorite.
A dispersive prism can be used to break light up into its constituent spectral colors
(the colors of the rainbow). Furthermore, prisms can be used to reflect light, or to
split light into components with different polarizations. A plastic prism
Contents
How prisms work
Deviation angle and dispersion
History
Types of prisms
Dispersive prisms
Reflective prisms
Beam-splitting prisms
Polarizing prisms
Deflecting prisms
In optometry
See also
References
Further reading
External links
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If the angle of incidence and prism apex angle are both small, and if the angles are
expressed in radians. This allows the nonlinear equation in the deviation angle to be approximated by
The deviation angle depends on wavelength through n, so for a thin prism the deviation angle varies with wavelength
according to
History
René Descartes had seen light separated into the colors of the rainbow by glass or water,[1] though the source of the
color was unknown. Isaac Newton's 1666 experiment of bending white light through a prism demonstrated that all the
colors already existed in the light, with different color "corpuscles" fanning out and traveling with different speeds
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through the prism. It was only later that Young and Fresnel combined Newton's
particle theory with Huygens' wave theory to explain how color arises from the
spectrum of light.
Newton arrived at his conclusion by passing the red color from one prism through a
second prism and found the color unchanged. From this, he concluded that the
colors must already be present in the incoming light — thus, the prism did not
create colors, but merely separated colors that are already there. He also used a lens
and a second prism to recompose the spectrum back into white light. This
experiment has become a classic example of the methodology introduced during the
scientific revolution. The results of the experiment dramatically transformed the
field of metaphysics, leading to John Locke's primary vs secondary quality A triangular prism,
distinction. dispersing light
Newton discussed prism dispersion in great detail in his book Opticks.[2] He also
introduced the use of more than one prism to control dispersion.[3] Newton's description of his experiments on prism
dispersion was qualitative. A quantitative description of multiple-prism dispersion was not needed until multiple
prism laser beam expanders were introduced in the 1980s.[4]
Types of prisms
Dispersive prisms
Dispersive prisms are used to break up light into its constituent spectral colors
because the refractive index depends on frequency; the white light entering the
prism is a mixture of different frequencies, each of which gets bent slightly
differently. Blue light is slowed down more than red light and will therefore be bent
more than red light.
Triangular prism
Abbe prism
Pellin–Broca prism
Amici prism
Compound prism
Grism, a dispersive prism with a diffraction grating on its surface
Porro prism
Porro–Abbe prism
Amici roof prism
Pentaprism and roof pentaprism
Abbe–Koenig prism
Schmidt–Pechan prism
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Bauernfeind prism
Dove prism
Retroreflector prism
Beam-splitting prisms
Some reflective prisms are used for splitting a beam into two or more beams:
Polarizing prisms
There are also polarizing prisms which can split a beam of light into components of varying polarization. These are
typically made of a birefringent crystalline material.
Nicol prism
Wollaston prism
Nomarski prism – a variant of the Wollaston prism with advantages in microscopy
Rochon prism
Sénarmont prism
Glan–Foucault prism
Glan–Taylor prism
Glan–Thompson prism
Deflecting prisms
Wedge prisms are used to deflect a beam of light by a fixed angle. A pair of such prisms can be used for beam steering;
by rotating the prisms the beam can be deflected into any desired angle within a conical "field of regard". The most
commonly found implementation is a Risley prism pair.[5] Two wedge prisms can also be used as an anamorphic pair
to change the shape of a beam. This is used to make a round beam from the elliptical output of a laser diode.
Rhomboid prisms are used to laterally displace a beam of light without inverting the image.
Deck prisms were used on sailing ships to bring daylight below deck,[6] since candles and kerosene lamps are a fire
hazard on wooden ships.
In optometry
By shifting corrective lenses off axis, images seen through them can be displaced in the same way that a prism
displaces images. Eye care professionals use prisms, as well as lenses off axis, to treat various orthoptics problems:
In contrast, spectacles with prisms of equal power for both eyes, called yoked prisms (also: conjugate prisms,
ambient lenses or performance glasses) shift the visual field of both eyes to the same extent.[7]
See also
Minimum deviation
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References
1. James Gleick (June 8, 2004). Isaac Newton. Vintage. ISBN 1400032954.
2. Isaac Newton (1704). Opticks. London: Royal Society. ISBN 0-486-60205-2.
3. "The Discovery of the Spectrum of Light" (http://www.juliantrubin.com/bigten/lightexperiments.html). Retrieved
19 December 2009.
4. F. J. Duarte and J. A. Piper (1982). "Dispersion theory of multiple-prism beam expanders for pulsed dye lasers".
Opt. Commun. 43 (5): 303–307. Bibcode:1982OptCo..43..303D (http://adsabs.harvard.edu/abs/1982OptCo..43..3
03D). doi:10.1016/0030-4018(82)90216-4 (https://doi.org/10.1016%2F0030-4018%2882%2990216-4).
5. Duncan, B.D.; Bos, P.J.; Sergan, V. (2003). "Wide-angle achromatic prism beam steering for infrared
countermeasure applications" (https://works.bepress.com/philip_bos/56/download/). Opt. Eng. 42 (4): 1038–1047.
Bibcode:2003OptEn..42.1038D (http://adsabs.harvard.edu/abs/2003OptEn..42.1038D). doi:10.1117/1.1556393 (ht
tps://doi.org/10.1117%2F1.1556393).
6. Loenen, Nick (February 2012). Wooden Boat Building: How to Build a Dragon Class Sailboat (https://books.googl
e.com/books?id=9T1tjjteQesC&pg=PA120&dq=Deck+prisms+were+used+on+sailing+ships+to+bring+daylight+b
elow+deck&hl=en&sa=X&ved=0ahUKEwiprcLLm6rXAhUQ02MKHTC_BwMQ6AEIJjAA#v=onepage&q=Deck%20
prisms%20were%20used%20on%20sailing%20ships%20to%20bring%20daylight%20below%20deck&f=false).
FriesenPress. ISBN 9781770974067.
7. Kaplan, M; Carmody, D. P.; Gaydos, A (1996). "Postural orientation modifications in autism in response to
ambient lenses". Child Psychiatry and Human Development. 27 (2): 81–91. PMID 8936794 (https://www.ncbi.nlm.
nih.gov/pubmed/8936794).
Further reading
Hecht, Eugene (2001). Optics (4th ed.). Pearson Education. ISBN 0-8053-8566-5.
External links
"Prism" (https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Prism). Encyclopædia
Britannica. 22 (11th ed.). 1911. p. 361.
Java applet of refraction through a prism (http://www.phy.hk/wiki/englishhtm/RefractionByPrism.htm)
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