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: 692
disperse
  پاشیدن   
pâšidan (#)

Fr.: disperser   

1) To spread or distribute from a fixed or constant source.
2) To become dispersed.

M.E., from M.Fr. disperser "scatter," from L. dispersus, p.p. of dispergere "to scatter," from → dis- "apart" + spargere "to scatter," from PIE base *(s)pregh- "to scatter;" cf. Av. spareg- "to germinate, shoot, sprout," fra-sparəγa- "shoot, sprout," Skt. parjanya- "rain, rain god," Lith. spurgas "sprout."

Pâšidan "to scatter, sprinkle," az ham pâšidan "to scatter on all sides;" cf. Gazi pâšn-/pâšnâ "to scatter, spread," Lor. perxa "sprinkling;" Av. paršat.gauu- "having a speckled cow;" Skt. prs- "to sprinkle," parsati "sprinkles;" Toch. pärs- "to sprinkle;" Lith. purškiu "I spray;" PIE roor *pers- "to spray, sprinkle."

dispersion
  پاشش   
pâšeš (#)

Fr.: dispersion   

1) The resolution of white light into its component wavelengths, either by → refraction or by → diffraction. Dispersion is actually an effect in which radiations having → different wavelengths travel at different speeds in the medium. Since the → angle of refraction of each radiation vary as a function of its → wavelength, the component waves deviate from each other.
2) The rate of change of → refractive index with wavelength: dn/dλ. → Cauchy's equation shows that dispersion varies approximately as the inverse cube of the wavelength.
3) The selective → retardation of → radio waves when they propagate through a → plasma. As a result, higher → frequency waves from a → pulsar will arrive at the Earth before the lower frequencies due to the presence of → intervening → ionized gas in the → interstellar medium. → dispersion measure.
4) Statistics: The spread of values of a → variable around the → mean or → median of a → distribution.

Verbal noun of → disperse.

dispersion curve
  خم ِ پاشش   
xam-e pâšeš

Fr.: courbe de dispersion   

A graph displaying the variation of the → refractive index of a substance against the wavelength of the electromagnetic wave passing through the substance.

dispersion; → curve.

dispersion equation
  هموگش ِ پاشش   
hamugeš-e pâšeš

Fr.: équation de dispersion   

An equation representing the variation of → refractive index as a function of → wavelength; for example → Cauchy's equation and → Sellmeier's equation.

dispersion; → equation.

dispersion measure
  اندازه‌ی ِ پاشش   
andâze-ye pâšeš

Fr.: mesure de dispersion   

A parameter used in radio astronomy which describes the amount of dispersion in a radio signal due to its passage through an intervening plasma. It is proportional to the product of the interstellar electron density and the distance to the source.

dispersion; → measure.

dispersion relation
  بازانش ِ پاشش   
bâzâneš-e pâšeš

Fr.: relation de dispersion   

An equation that describes how the → angular frequency, ω, of a wave depends on its → wave number, k. For the simplest of waves, where the speed of propagation, c, is a constant, ω(k) = ck. If the → phase velocity depends on k, that is for a dispersive medium, the function ω(k) is nonlinear.

dispersion; → relation.

dispersive
  پاشنده، پاششی   
pâšandé, pâšeši

Fr.: dispersif   

Tending or serving to disperse.

From → disperse + → -ive.

dispersive index
  دیشن ِ پاششی   
dišan-e pâšeši

Fr.: indice de dispersion   

The reciprocal of the → dispersive power.

dispersive; → index.

dispersive medium
  مدیم ِ پاشنده   
madim-e pâšandé

Fr.: milieu dispersif   

A medium in which the → phase velocity is a function of → wave number (→ frequency).

dispersive; → medium.

dispersive power
  توان ِ پاشش   
tâvân-e pâšeš

Fr.: pouvoir dispersif   

A measure of the ability of a medium to separate different colors of light. It is defined by: (n2 - n1)/(n - 1), where  n1 and n2 are refractive indices at two specified widely differing wavelengths, and n is the → index of refraction for the average of these wavelengths.

dispersive; → power.

displacement
  جا-به-جایی   
jâ-be-jâyi (#)

Fr.: déplacement   

Physics: A vector quantity that specifies the change of position of a body or particle from the mean position or position of rest.
Geology: The offset of rocks caused by movement along a fault.

From displace, from → dis- + place + -ment.

Jâ bé jâyi, noun of jâ bé jâ literally "place to place," from "place," from Mid.Pers. giyag "place," O.Pers. ā-vahana- "place, village," Av. vah- "to dwell, stay," vanhaiti "he dwells, stays," Skt. vásati "he dwells," Gk. aesa (nukta) "to pass (the night)," Ossetic wat "room; bed; place," Tokharian B wäs- "to stay, wait;" PIE base ues- "to stay, live, spend the night."

displacement current
  جریان ِ جا-به-جایی   
jarayân-e jâ-be-jâyi (#)

Fr.: courant de déplacement   

In electromagnetism, a quantity which is not a real current (movement of charge), but has the units of current and has an associated magnetic field. The physical meaning of this displacement current is that a changing electric field makes a changing magnetic field.

displacement; → current.

display
  ۱) نمودن، نمایاندن، نمایش‌دادن؛ ۲) نمایش   
1) nemudan, nemâyândan, nemâyeš dâdan; 2) nemâyeš (#)

Fr.: 1) visualiser; 2) visualisation   

1a) To show; make visible.
1b) Of computers, to show the output data on a screen.
2a) The act of displaying.
2b) Of computers, a visual representation of information.

From O.Fr. despleier "to unfold, spread out," from L. displicare "to scatter," from → dis- "un-, apart" + plicare "to fold, twist," from PIE base *plek- "to plait, twist" (cf. Gk. plekein "to plait," L. plectere "to plait, braid, intertwine," Av. frašna- "helmet" (in ərəzatô.frašna- "having a silver helmet" (epithet of Mithra), Skt. praśna- "turban," O.H.G. flehtan "to plait," Russ. plesti "to plait").

Nemudan, nemâyândan "to show, display," from Mid.Pers. nimūdan, present stem nimây- "to show," from O.Pers./Av. ni- "down; into," → ni-, + māy- "to measure," cf. Skt. mati "measures," matra- "measure," PIE base *me- "to measure;" cf. Gk. metron "measure," L. metrum.

displease
  وازوشیدن   
vâzušidan

Fr.: déplaire   

1) To incur the dissatisfaction, dislike, or disapproval of; offend; annoy.
2) To be unpleasant; cause displeasure (Dictionary.com).

dis-; → please.

displeasure
  وازوشه   
vâzušé

Fr.: mécontentement, déplaisir   

Dissatisfaction, disapproval, or annoyance.

dis-; → pleasure.

disruption
  گسیخت   
gosixt

Fr.: rupture   

Forcible division into pieces of an object. → tidal disruption.

From L. disruptio "a breaking asunder," noun of action from p.p. stem of disrumpere "break apart, split, shatter, break to pieces," from → dis- "apart" + rumpere "to break."

Gosixt, past stem of gosixtan "to tear away, to beark off."

dissect
  واسکنجیدن   
vâsekanjidan

Fr.: disséquer   

1) To cut apart (an animal body, plant, etc.) to examine the structure, relation of parts, or the like.
2) To examine minutely part by part; analyze: to dissect an idea (Dictionary.com).

L. dissectus, p.p. of dissecare "to cut to pieces," from dissecare "cut in pieces," from → dis- "apart" + secare "to cut," → section.

Vâsekanjidan, from vâ- "apart," → dis-, + sekanjidan "to cut to pices," cognate with šekastan "to break," → section.

dissection
  واسکنجش   
vâsekanješ

Fr.: dissection   

The act of dissecting.

dissect; → -tion.

dissipate
  افتالیدن   
eftâlidan

Fr.: dissiper   

1) To scatter in various directions. To spend or use wastefully.
2) To cause to lose (energy, such as heat) irreversibly. See also: → dissipation, → dissipative.

From L. dissipatus, p.p. of dissipare "to disperse, squander," from → dis- "apart" + supare "to throw, scatter."

Eftâl, eftâleš, from eftâlidan "to disperse; to tear; to break," ultimately from Proto-Ir. *abi-tard-, from *tard- "to pierce, split;" cf. Skt. tard- "to split, pierce, open;" Lith. trandéti "to be eaten by moths or worms;" PIE base *terd- "to pierce" (Cheung 2007).

dissipation
  افتال، افتالش   
eftâl, eftâleš

Fr.: dissipation   

The loss of energy over time by a → dynamical system, typically due to the action of → friction or → turbulence. The lost energy is converted into heat, raising the temperature of the system. See also: → Ohmic dissipation. → viscous dissipation.

Noun form of → dissipate.

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