An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 13176 Search : far
optical density
  چگالیِ نوری   
cagâli-ye nuri

Fr.: densité optique   

The transmittance of a point on a photographic negative equal to the log to the base 10 of the reciprocal of the transmittance through the negative at that point.

optical; → density.

optical depth
  ژرفایِ نوری   
žarfâ-ye nuri

Fr.: profondeur optique   

1) A measure of how much radiation is absorbed when traveling through a medium (such as the atmosphere of a star or the interstellar medium) from the source to a given point. It depends on the type of medium and the frequency of radiation. It is defined as a dimensionless quantity λ = κλ ρ dx, where κλ is the extinction coefficient, ρ the density, and dx the path length.
2) The ratio of the intensity of radiation (light or radio waves) incident on a ring to that emerging from the opposite face of the ring, expressed as a natural logarithm. If the reduction in intensity is by a factors of e (= 2.718), the ring is said to have an optical depth of 1. Normal (or normalized) optical depth is optical depth corrected for oblique (non-vertical) viewing. In ring studies, the terms optical depth and optical thickness are generally used interchangeably. These terms generally refer to a particular wavelength (Ellis et al., 2007, Planetary Ring Systems, Springer).

optical; → depth.

optical double star
  ستاره‌یِ دوتایی ِ دیدگانی   
setâre-ye dotâyi-ye didgâni

Fr.: étoile double optique   

A pair of stars that lie close to each other in the sky by chance, but are not physically associated, in contrast to a true → binary star.

optical; → double star.

optical fiber
  فیبرِ نوری   
fibr-e nuri

Fr.: fibre optique   

A thin filament of drawn or extruded glass or plastic having a central core and a cladding of lower index material to promote internal reflection. It may be used singly to transmit pulsed optical signals (communications fiber) or in bundles to transmit light or images.

optical; → fiber.

optical illusion
  سفمانِ دیدگانی   
safmân-e didgâni

Fr.: illusion d'optique   

A perception of visual stimuli in which what is perceived is in a way different from the way it is in reality. Same as visual illusion.

optical; → illusion.

optical instrument
  سازالِ نوری   
sâzâl-e nuri

Fr.: instrument optique   

An instrument that either processes light waves to enhance an image or analyzes light waves to determine one of a number of characteristic properties.

optical; → instrument.

optical jet
  شان ِ نوری   
šân-e nuri

Fr.: jet optique   

An → astrophysical jet which is visible in the optical range of the electromagnetic radiation.

optical; → jet.

optical oblateness
  پخی ِ نوری   
paxi-ye nuri

Fr.: aplatissement optique   

(polar flattening) The ratio of the difference between equatorial and polar diameters to the equatorial diameter. A sphere has an oblateness of 0; an infinitely thin disk has an oblateness of 1 (Ellis et al., 2007, Planetary Ring Systems, Springer).

optical; → oblateness.

optical path
  راهِ نوری   
râh-e nuri (#)

Fr.: chemin optique   

In → geometric optics, the distance a light ray would travel in a vacuum in the same time it travels from one point to another, a specified distance, through one or more optical media.

optical; → path.

optical pulsar
  پولسارِ نوری، تپار ِ ~   
pulsâr-e nuri, tapâr-e ~

Fr.: pulsar optique   

A member of a rare class of pulsars, such as the → Crab pulsar and → Vela pulsar, which can be detected in the visible spectrum.

optical; → pulsar.

optical pumping
  پمپشِ نوری   
pompeš-e nuri

Fr.: pompage optique   

A process in which light energy is used to raise electrons from a lower energy level in an atom or molecule to a higher one. It is commonly used in laser construction, to pump the active laser medium so as to achieve population inversion. The technique was developed by 1966 Nobel Prize winner Alfred Kastler in the early 1950's.

optical; → pumping.

optical system
  راژمان ِ نوری، ~ نوریک   
râžmân-e nuri, ~ nurik

Fr.: système optique   

A collection of lens, prisms, mirrors, and/or other devices, placed in some specified configuration, to act on light (reflect, refract, disperse, polarize, etc.) and perform some definite optical function.

optical; → system.

optical thickness
  ستبرایِ نوری   
setabrâ-ye nuri

Fr.: épaisseur optique   

Same as → optical depth.

optical; → thickness.

optical transfer function (OTF)
  کریا‌یِ تراوژ ِ نوری   
karyâ-ye tarâvaž-e nuri

Fr.: fonction de transfert optique   

The function that provides a full description of the imaging quality of an optical system. A combination of the → modulation transfer function (MTF) and the → phase transfer function (PTF) , the OTF describes the spatial (angular) variation as a function of spatial (angular) frequency.

optical; → transfer; → function.

optical window
  روزنه‌یِ نوری   
rowzane-ye nuri

Fr.: fenêtre optique   

The optical portion of the electromagnetic spectrum that passes through the atmosphere all the way to the ground.

optical; → window.

optically
  نورانه، نوریکانه   
nurâné, nurikâné

Fr.: optiquement   

Adverb of → optical.

optical + -ly.

Nurâné, from nur, → light, + -âné "-ly;" nurikâné, from nurik, → optical, + -âné "-ly."

optically active
  نورانه ژیرا   
nurâné žirâ

Fr.: optiquement actif   

Relating to → optical activity.

optically; → active.

optically thick
  نورانه ستبر، نوریکانه ~   
nurâné setabr, nurikâné ~

Fr.: optiquement épais   

The qualifier of a medium in which the → optical depth is large, significantly larger than 1.

optically; → thick.

optically thick wind
  باد ِ نورانه ستبر   
bâd-e nurâné setabr

Fr.: vent optiquement épais   

A wind with the → sonic point located at large optical depth for continuum. In particular, → Wolf-Rayet star winds are → optically thick. However, the outer parts of W-R winds are → optically thin for continuum, and in those regions the matter flow is driven by the same mechanism as in the winds of OB stars.

optically; → thick; → wind.

optically thin
  نورانه تنک، نوریکانه ~   
nurâné tonok, nurikâné ~

Fr.: optiquement mince   

The qualifier of a medium in which the → optical depth is large, significantly smaller than 1.

optically; → thin.


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<< < -es -it -sc 201 951 abe abs abs aca acc acc aco act ada adh ado aer aft air Alf alg alk alp Alt alt amb ana And ang ani ann ant ant ant apo app app Apu arc arg Arn art ass ast ast ast atm ato att aur aut avo azi bac bal bar bar bat Bea Bel bet bia big bin bio Bir bla bla blo Blu bol Boo bou box bre Bri bro bur cal cal Can cap car Car cat cau cel cen cen cha Cha cha che Chi chr cir cir civ cla clo clo CMB coa coe coh col col col com com com com com com com com Com con con con con con con con con con con con con coo cor cor cor Cos cos cos cou cou cra cri cro cry cul cur cyc D l dar dat day dea dec dec dec def def deg Del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis diu dog Dop dou Dra Dsc dus dwa dyn Dys Ear ecc eco edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ eru eth Eur eve exa exc exe exi exo exp ext ext ext fab fai Fan fea fem fer fie fil fir fir fla fli flu foc for for for fra fre fre fri fun fuz gal gal gal Gam gau Gau gen geo geo geo geo Gib glo gov gra gra gra gra gre gro Gui H-a hal Ham har Hay hea hei hel Hel her het hie hig hoa hom hor hot Hub Hug hur hyd hyd hyl hyp ice ide ima ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv inv ion iro Isl iso iso Jab jet Jov Jup Kar Kep kil Kip Kra Lag Lam Lan Lar las law lea Leg Leo lev lig lim lin lin lin lit loc loc log Lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal map mas mas mat Mau mea mea med Men mer Mes Met met mic mic Mie mil min Mir mix mod mol mom Moo mor mov mul mur n-b nan nat nea neg Ner neu new New NGC noc nom non non nor nor nuc nuc nul nut obj obl obs occ oct off old one ope opp opt opt orb ord org Ori osc oth ove Owl P-s Pal par par par par Pas pat pec pen per per per per per Pha pha pho pho pho phy pie pix Pla pla pla pla Pli Poi pol pol pol pol por pos pos pow pre pre pre pre pri pri pri pro pro pro pro pro pro pro pub pul pyc qua qua qua qua qui rad rad rad rad rad rad rai ran rar Ray rea Rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot rur S5- Sal sat sca sca Sch sci Scu sec sec sed sel sel sem seq set sha she sho sid sie sil sim sin sit sky slo sno sod sol sol sol sol son sou spa spa spe spe spe spe sph spi spo squ sta sta sta sta ste ste ste Sti sto str str sub sub sub sul sup sup sup sup sur sur syl syn sys tal Tay tel ten ter tex the the the the Tho thr tid tim Tit too Tor tra tra Tra tra Tra tri Tri tru tub tur two Typ ult ult unc uni uni uni upl ura uti val var vec vel ver Ver vie vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>