Nicol prism

Nicol prism
A Nicol prism

A Nicol prism is a type of polarizer, an optical device used to produce a polarized beam of light from an unpolarized beam. See polarized light. It was the first type of polarizing prism to be invented, in 1828 by William Nicol (1770–1851) of Edinburgh. It consists of a rhombohedral crystal of Iceland spar (a variety of calcite) that has been cut at an angle of 68° with respect to the crystal axis, cut again diagonally, and then rejoined as shown using, as a glue, a layer of transparent Canada balsam.

Unpolarized light enters through the left face of the crystal, as shown in the diagram, and is split into two orthogonally polarized, differently directed, rays by the birefringence property of the calcite. One of these rays (the ordinary or o-ray) experiences a refractive index of no = 1.658 in the calcite and it undergoes total internal reflection at the calcite-glue interface because its angle of incidence at the glue layer (refractive index n = 1.55) exceeds the critical angle for the interface. It passes out the top side of the upper half of the prism with some refraction as shown. The other ray (the extraordinary ray or e-ray) experiences a lower refractive index (ne = 1.486) in the calcite, and is not totally reflected at the interface because it strikes the interface at a sub-critical angle. The e-ray merely undergoes a slight refraction, or bending, as it passes through the interface into the lower half of the prism. It finally leaves the prism as a ray of plane polarized light, undergoing another refraction as it exits the far right side of the prism. The two exiting rays have polarizations orthogonal (at right angles) to each other, but the lower, or e-ray, is the more commonly used for further experimentation because it is again traveling in the original horizontal direction, assuming that the calcite prism angles have been properly cut. The direction of the upper ray, or o-ray, is quite different from its original direction because it alone suffers total internal reflection at the glue interface as well as a final refraction on exit from the upper side of the prism.

Nicol prisms were once widely used in microscopy and polarimetry, and the term "using crossed Nicols" (abbreviated as XN) is still used to refer to the observing of a sample placed between orthogonally oriented polarizers. In most instruments, however, Nicol prisms have been replaced by other types of polarizers such as Polaroid sheets and Glan–Thompson prisms.

See also


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Look at other dictionaries:

  • Nicol prism — Prism Prism (pr[i^]z m), n. [L. prisma, Gr. pri sma, fr. pri zein, pri ein, to saw: cf. F. prisme.] 1. (Geom.) A solid whose bases or ends are any similar, equal, and parallel plane figures, and whose sides are parallelograms. [1913 Webster] Note …   The Collaborative International Dictionary of English

  • Nicol prism — or Nicol [nik′əl] n. [after Wm. Nicol (1768? 1851), Brit physicist, who invented it (1828)] a prism consisting of two crystals of clear calcite cemented together, used for obtaining polarized light …   English World dictionary

  • Nicol prism — Nikolio prizmė statusas T sritis fizika atitikmenys: angl. Nicol prism vok. Nicolprisma, n; Nicolsches Prisma, n rus. призма Николя, f pranc. prisme de Nicol, m …   Fizikos terminų žodynas

  • Nicol prism — Nic·ol prism (nikґol) [William Nicol, Scottish physicist, 1768–1851] see under prism …   Medical dictionary

  • Nicol prism — [ nɪk(ə)l] noun a prism for producing plane polarized light, consisting of two pieces of optically clear calcite cemented together with Canada balsam. Origin C19: named after the Scottish physicist William Nicol …   English new terms dictionary

  • Nicol prism — /nik euhl/, Optics. one of a pair of prisms used to produce and analyze plane polarized light in a polarizing microscope. Also called Nicol. Cf. polarizer (def. 1). [1870 75; after William Nicol (1768 1851), British physicist, its inventor] * * * …   Universalium

  • Nicol prism — noun An optical device used to generate polarized light. “You are in mortal danger,” declared their Scientific Officer, Dr. Counterfly, a scholarly sort, bearded and bundled like the rest of them, his eyes concealed by a pair of ingenious goggles …   Wiktionary

  • Nicol prism — two slabs of Iceland spar cemented together and deflecting a ray of light in such a way that it is split in two, one part (the ordinary ray) being totally reflected and the other (polarized ray) passing through …   Medical dictionary

  • Nicol prism — noun optical device that produces plane polarized light • Hypernyms: ↑optical device …   Useful english dictionary

  • Nicol's prism — Prism Prism (pr[i^]z m), n. [L. prisma, Gr. pri sma, fr. pri zein, pri ein, to saw: cf. F. prisme.] 1. (Geom.) A solid whose bases or ends are any similar, equal, and parallel plane figures, and whose sides are parallelograms. [1913 Webster] Note …   The Collaborative International Dictionary of English

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