Bohr's first postulate 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's postulate 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's second postulate 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's third postulate 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 = ε_{1} - ε_{2}, where h is the → Planck's constant and ν the frequency of the transition. |
Clausius's postulate 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 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. |
Planck postulate 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. |
postulate 1) farâvas; 2) farâvasidan Fr.: 1) postulat; 2) postuler 1a) 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. 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;" cf. O.Pers. vasiy
"at will, greatly, utterly," vašna- "will, favor;"
Mid.Pers. vasnâd "because, on account of."
This word is extant in several Modern Iranian
dialects: Tabari vessen "to wish, desire," Gilaki vâssan
"to wish, desire," vâsti "desire; for, because, on account of;"
Kurd. wistin "to desire, wish," Lâri avessa "to desire;"
Nâyini vas "to like;" colloquial
Tehrâni vâsé "for;"
Lori, Malâyeri biza "pregnancy craving;"
cognate with Skt. vaś- "to wish, want, desire," váśa-
"wish, desire," vasēna "for, because;" Gk. ekon "voluntary;"
PIE base *uek- "to wish." |