An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

→ prism angle.

→ angle; → prism.

A combination of two 30° prisms, one of left-handed quartz and the other of right-handed quartz. The prisms are cemented together in order to get a 60° prism. The device will correct for light rotation and will transmit the beam in a straight direction. The Cornu prism has good ultraviolet transmitting qualities and no → double refraction.

→ Cornu's spiral; → prism.

An optical element consisting of two small angle → prisms, joined together at their bases, used to produce two → coherent sources. The thin double prism refracts the light from a source into two overlapping beams, which produce → interference fringes. With this experiment Fresnel was able to produce interference without relying upon → diffraction to bring the interfering beams together.

→ Fresnel diffraction; → bi-; → prism.

A prism having angles of 30, 60, and 90°, which uses the same face for input and dispersed radiation. The beam is reflected at the face opposite to the 60° angle because it is coated to be highly reflecting. A beam entering at the → Brewster angle undergoes minimum deviation and hence maximum dispersion. Littrow prisms are used in laser cavities to fine tune lasers by selection of wavelength.

Joseph Johann Littrow (1781-1840), Austrian astronomer; → prism.

Optical device constructed from a crystal of calcite, used for obtaining plane polarized light.

Named after John Pringle Nicol (1804-1859), British physicist; → prism.

A dispersing prism placed in front of a telescope objective to produce spectra of all luminous objects in the field of view.

→ objective; → prism.

A prism that is used to produce or analyze plane-polarized light.

Polarizing, adj. of → polarize; → prism.

Optics: A transparent solid body, having at least two polished plane faces inclined relative to each other, from which light is reflected or through which light is refracted.
Geometry: A solid having two faces lying in parallel planes and with the other faces parallelograms.

L.L. prisma, from Gk. prisma, literally "something sawed," from prizein "to saw."

Manšur, etymology not clear, may be related to Ar. mawšur "prism," of unknown origin.

The angle between the faces on which light is incident and from which it emerges.

→ prism; → angle.

An optical device consisting of a pair of small telescopes mounted side by side, each telescope having two prisms between the eyepiece and objective for erecting the image.

→ prism; → binoculars.

An ocular equipped with a prism that forms an upright image in an astronomical telescope.

→ prism; → ocular.

An instrument used to determine the precise timing of a star's passage across a vertical circle. It is used for making precise determinations of the positions of stars and planets, and can be used inversely to determine the latitude and longitude of the observer, assuming the star positions are accurately known. It consists of an accurate prism, a small pool of mercury to serve as an artificial horizon. The most notable example of this type of instrument is that of → Danjon astrolabe.

Adj. of → prism + → astrolabe.

The spectrum formed by a dispersing prism or a dispersing prism system.

Adj. of → prism + → spectrum.

A prism that is used as a dispersing element in a spectrograph.

→ refracting; → prism.

An optical device for producing and analyzing polarized light. It divides incoming unpolarized light into two orthogonal, linearly polarized beams. It consists of two prisms of either quartz or calcite cemented together.

After the English scientist William Hyde Wollaston (1766-1828); → prism.