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: 8 Search : postulate
Bohr's first postulate
  فراوس ِ نخست ِ بؤر   
farâvas-e naxost-e Bohr

Fr.: premier postulat de Bohr   

One of the postulates used in the → Bohr model, whereby there are certain steady states of the atom in which electrons can only travel in stable orbits. In spite of their acceleration, the electrons do not radiate electromagnetic waves when they move along stationary orbits.

Bohr; → first; → postulate.

Bohr's postulate
  فراوس ِ بؤر   
farâvas-e Bohr

Fr.: postulat de Bohr   

One of the three postulates advanced in the → Bohr model which led to the correct prediction of the observed line spectrum of hydrogen atom. See also → Bohr's first postulate, → Bohr's second postulate, → Bohr's third postulate,

Bohr; → postulate.

Bohr's second postulate
  فراوس ِ دوم ِ بؤر   
farâvas-e dovom-e Bohr

Fr.: deuxième postulat de Bohr   

One of the postulates used in the → Bohr model, whereby when an atom is in the steady state an electron travelling in a circular orbit should have → quantized values of the → angular momentum which comply with the condition p = n(h/2π), where p is the angular momentum of the electron, h is → Planck's constant, and n is a positive integer called → quantum number.

Bohr; → second; → postulate.

Bohr's third postulate
  فراوس ِ سوم ِ بؤر   
farâvas-e sevom-e Bohr

Fr.: troisième postulat de Bohr   

One of the postulates used in the → Bohr model, whereby the atom emits (absorbs) a quantum of electromagnetic energy (→ photon) when the electron passes from an orbit with a greater (lesser) n value to one with a lesser (greater) value. The energy of the quantum is equal to the difference between the energies of the electron on its orbits before and after the transition or "jump": hν = ε1 - ε2, where h is the → Planck's constant and ν the frequency of the transition.

Bohr; → third; → postulate.

Clausius's postulate
  فراوس ِ کلاؤزیوس   
farâvas-e Clausius

Fr.: postulat de Clausius   

If heat flows by conduction from body A to another body B, then a transformation whose only final result is to transfer heat from B to A is impossible. Clausius's postulate is a formulation of the → second law of thermodynamics. It is also equivalent to → Kelvin's postulate.

Clausius equation; → postulate.

Kelvin's postulate
  فراوس ِ کلوین   
farâvas-e Kelvin

Fr.: postulat de Kelvin   

A transformation whose only final result is to transform into work heat extracted from a source which is at the same temperature is impossible. Kelvin's postulate is a statement of the → second law of thermodynamics and is equivalent to → Clausius's postulate.

kelvin; → postulate.

Planck postulate
  فراوَس ِ پلانک   
farâvas-e Planck

Fr.: postulat de Planck   

The postulate that the energy of oscillators in a blackbody is quantized by E = nhν, where n = 1, 2, 3, ..., h is Planck's constant, and ν the frequency.

Planck; → postulate.

postulate
  ۱) فراوس؛ ۲) فراوسیدن   
1) farâvas; 2) farâvasidan

Fr.: 1) postulat; 2) postuler   

1) Math.: An unproved assumption taken as basic in a mathematical system, and from which (in combination with other postulates) the propositions of the system are derived, or in terms of which the propositions are proved. In modern usage, postulate is synonymous with → axiom.
Physics: A fundamental principle. For example, the two postulates of special relativity of Einstein are: 1) The laws of physical phenomena are the same when studied in terms of two reference systems moving at a constant velocity relative to each other. 2) The velocity of light in free space is the same for all observers and is independent of the relative velocity of the source of light and the observer. See also → Planck postulate.
2) General: To ask, demand, or claim. To claim or assume the existence or truth of, especially as a basis for reasoning or arguing.
Math.: To assume as a postulate.

From L. postulatum "petition, thing requested," noun use of neuter of p.p. of postulare "to ask, request, demand," akin to poscere "to request."

Farâvas (on the model of piš-nahâd "proposition," and farâ-nemudan "to exhibit, expose"), from farâ-, → pro-, + vas. The second component from Av. vas- "to will, desire, wish, long for," vasəmi "I wish," vasna- "will, favor," ušti- "desire, wish, will," vasô, vasə "at one's will." This word is extant in several Mod.Pers. dialects, Tabari vessen "to wish, desire," Gilaki vâssan "to wish, desire," vâsti "desire," Kurd. wistin "to desire, wish," Lâri avessa "to desire," colloquial Tehrâni vâsé "for" (Mid.Pers. vasnâd "because"); O.Pers. vasiy "at will, greatly, utterly," vašna- "will, favor;" cf. Skt. vaś- "to wish, want, desire," váśa- "wish, desire," vasēna "for, because;" Gk. ekon "voluntary;" PIE base *uek- "to wish."