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: 13116 Search : far
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.

optically violent variable (OVV) quasar
  کو‌آسارِ ورتنده‌ی ِ نورانه سورا   
kuâsâr-e vartande-ye nurâné surâ

Fr.: quasar variable optiquement violent   

A member of a small subset of quasars consisting of bright radio galaxies whose flux of visible light output can vary by as much as 50% in a single day.

optically; → violent; → variable; → quasar.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer aga air Alf Alg alk Alp alt alu amm ana And ang ani ano ant ant Ap apo app app Aqu Arc arg arr asc ass ast ast asy atm ato att aur aut axi B-m bad Bal bar bar Bay Bed ber Bet bif bim bin bio bis bla ble blu Bod Bol bor bou Bra Bre bro bul C-t Cal Cam can car Car Cas cat cav cel cen cer Cha cha Cha che chl Cir cir cir Cla cli clo clu co- coc 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 Cre cri cro cub cur cyc cyl Dan dat Dav de- Deb dec dec dee def deg del Den den der det deu dew dic dif dif dil Dip dir dis dis dis dis dis diu dod Dop dou Dra dua dus dwa dyn DZ Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla Flo flu fog for for Fou fra fre fre Fro fun G s Gal gal gal Gar gau geg gen geo geo geo ger gla gly gra gra gra gra gra Gre gro GYR Had Hal hap Har HD hea hel hel Hen Her hex hig Hil hol Hoo hor hou Hub hum hyb hyd hyd hyp hys ide ign ima imp imp in- inc Ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jor jum K c Kep Ker kin kno lab Lam Lan Lap las lat Le lef len lev lig lig lin lin lin liq Lit loc log lon lou LS lun lun Lym M s Mag mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mol mon mor mov mul mur mys nan nat nav nec Nep neu New New NGC nob nom non non nor nos nuc nuc num nut obj obl obs occ oct off oli oni ope opp opt opt orb ord org orp osc out ove oxi P-w pal par par par par Pas pat pej per per per per per per pha Phe pho pho pho phy pin pla Pla pla pla pla plu poi pol pol Pol pol por pos pot Poy pre pre pre pre pri pri pri pro pro pro pro pro pro Psa pul pum Q i qua qua qua qua R A rad rad rad rad rad rad Ram Ran rat rea rea rec rec red red ref ref reg rei rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set Sha sha shi sho sid sig sim sin Sir ske sli Smo soc sof sol sol sol sol sou sou spa spe spe Spe spe sph spi Spi spr sta sta sta sta sta ste ste ste Sto str str sub sub sub suc sun sup sup sup sup sur swa syn syn tac tas tel tem ter tes the the the the thi thr tid til tip ton tor tou tra tra tra tra Tri tri tru tsu tur two Typ UHE ult unc uni uni uni upg 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 > >>