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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 15 Search : plate
compensator plate
  تیغه‌ی ِ پاهنگنده   
tiqe-ye pâhangandé

Fr.: compensatrice   

A transparent plate inserted in one of the arms of an interferometer, in particular the → Michelson interferometer, to compensate for a longer → optical path in the other arm. Its function is to ensure that the beams transverse the same total thickness of glass in both arms of the interferometer. This is not essential for producing → interference fringes in monochromatic light. The compensator plate is of the same glass and the same thickness as the → beam splitter plate.

compensator; → plate.

correcting plate
  تیغه‌ی ِ ارشاینده، ~ ارشاگر   
tiqe-ye aršâyandé, ~ aršâgar

Fr.: lame correctrice   

A large glass plate placed at the entrance of a Schmidt telescope to correct for spherical aberration over the large field of view.

correct; → plate.

half-wave plate
  تیغه‌ی ِ نیم‌موج   
tiqe-ye nin-mowj (#)

Fr.: lame demi-onde   

A plate of optical material whose thickness is such that the phase difference between the extraordinary and ordinary rays after passing through the place is exactly one-half cycle. It can serve to rotate the plane of polarization of a light beam.

half; → wave; → plate.

plane-parallel plate
  تیغه‌ی ِ تخت-پراسو   
tiqe-ye taxt-parâsu

Fr.: lame plan-parallèle   

A piece of glass with plane parallel surfaces used to admit light into an optical system and to exclude dirt and moisture.

plane; → parallel; → plate.

plate
  ۱) تیغه؛ ۲)؛ ۳) پلاک   
1) tiqé (#); 2); 3) pelâk (#)

Fr.: 1) lame; 2); 3) plaque   

1) Optics: Any crystalline material whose length is much less than its measured diameter. → half-wave plate.
2) A flat piece of material on which a picture or text has been produced.
3) Any of the large movable segments into which the Earth's lithosphere is divided. → plate tectonics.

M.E., from O.Fr. plate "thin piece of metal," from M.L. plata "plate, piece of metal," perhaps via V.L. *plattus, from Gk. platys " flat, broad."

1) Tiqé, from tiq "blade," related to tiz "sharp," variants tig, tež, tej, tij; Mid.Pers. tigr, têz, têž "sharp," O.Pers. tigra- "pointed," tigra.xauda- "pointed helmet (epithet of Scythians)," Av. tiγra- "pointed," tiγray- "arrow," tiži.arštay- "with the pointed spear," cf. Skt. tikta- "sharp, pungent, bitter," tejas- "sharpness, edge, point or top of a flame;" PIE base *st(e)ig- "to stick; pointed." Cognates in other IE languages: Gk. stizein "to prick, puncture," stigma "mark made by a pointed instrument," L. in-stigare "to goad," O.H.G. stehhan, Ger. stechen "to stab, prick," Du. stecken, O.E. sticca "rod, twig, spoon," E. stick.
2); 3) loanword from Fr., as above.

plate center
  مرکز ِ پلاک   
markaz-e pelâk

Fr.: centre de plaque   

The celestial coordinates of the center of the field of an astronomical photographic plate.

plate; → center.

plate scale
  مرپل ِ پلاک   
marpel-e pelâk

Fr.: échelle de plaque   

The scale factor for converting linear measure on a photographic plate to angular measurement on the sky.

plate; → scale.

plate tectonics
  سازانیک ِ پلاک   
sâzânik-e pelâk

Fr.: tectonique des plaques   

The theory supported by a wide range of evidence in which the Earth's crust is composed of several large, thin, relatively rigid plates that move relative to one another. The interaction of the plates at their boundaries causes seismic and tectonic activity along these boundaries. See also → continental drift.

plate; → tectonics.

plateau
  تختال   
taxtâl

Fr.: plateau   

1) An extensive area with a fairly level surface raised sharply above adjacent land.
2) A period, phase, or state of little or no growth or decline in something. → Spite plateau.

From Fr. plateau, from O.Fr. platel "flat piece of metal, wood, etc.," diminutive of plat "flat surface or thing," → plate.

Taxtâl, from taxt "flat;" Mid.Pers. taxtag "tablet, plank, (chess)board" + -âl, → -al.

platelet
  پلاکچه   
pelâkcé

Fr.: plaquette   

1) A small platelike body.
2) One of a variety of forms taken on by → snowflakes.
3) A tiny cell occurring in the blood of vertebrates and involved in clotting of the blood. Formerly called thrombocyte.

plate; → -let.

quarter-wave plate
  تیغه‌ی ِ چارک-موج   
tiqe-ye cârak-mowj

Fr.: lame quart d'onde   

A plate of doubly refracting material cut parallel to the optic axis of the crystal and of such a thickness that a phase difference of 90° is introduced between the ordinary and extraordinary rays for light of a particular wavelength. → half-wave plate.

quarter; → wave; → plate.

retardation plate
  تیغه‌ی ِ دیرکرد   
tiqe-ye dirkard

Fr.: lame à retard   

Same as → wave plate.

retardation; → plate.

Sachs-Wolfe plateau
  تختال ِ زاخس-وُلف   
taxtâl-e Sachs-Wolfe

Fr.: plateau de Sachs-Wolfe   

An almost horizontal region in the → CMB angular power spectrum belonging to a → multipole index 10 ≤ l ≤ 100. This feature is due to the → Sachs-Wolfe effect.

Sachs-Wolfe effect; → plateau.

Spite plateau
  تختال ِ اسپیت   
taxtâl-e Spite

Fr.: plateau des Spite   

The observation that the abundance of → lithium (7Li) in metal-poor stars is constant regardless of the → effective temperature (> 5500 K) and the → metallicity ([Fe/H] < -2). The Spite plateau is currently interpreted as evidence that the Li observed in → halo population stars is → primordial. Since its discovery, the Spite plateau has been subject to numerous investigations, increasing the number of stars with Li measurements and extending the sample to include ever lower metallicities. Important issues are the existence or not of a significant scatter along the plateau, and the existence or not of atomic diffusion and mixing with deeper stellar zones where Li can be burnt, producing an offset with respect to the → Big Bang → nucleosynthesis abundance. Several recent studies have shown that the Spite plateau exhibits very little, if any, dispersion. There is, however, a discrepancy between recent results and that derived from Big Bang nucleosynthesis, based on the cosmological parameters constrained by the → WMAP measurements.

Named after François and Monique Spite, French astronomers, Paris Observatory, who first discovered this relation (1982, A&A 115, 357); → plateau.

wave plate
  تیغه‌ی ِ موج   
tiqe-ye mowj (#)

Fr.: lame à retard   

An optical element that retards the phase of one plane of vibration of light relative to the plane at right angles. The two beams then recombine to form a single beam with new polarization characteristics. A typical wave plate is a birefringent crystal with a carefully chosen orientation and thickness. Also known as → retardation plate. A → half-wave plate creates a half-wave retardation. See also → quarter-wave plate.

wave; → plate.