# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 93 Search : equation
 acoustic wave equation   هموگش ِ موج ِ صدایی   hamugeš-e mowj-e sedâyiFr.: équation de l'onde acoustique   A → differential equation that describes the time evolution of the → scalar potential of the field φ. It is expressed by: ∇2φ = (1/c2)∂2φ/∂t2, where c is → velocity of → longitudinal waves and ∇2 is the → Laplacian operator.→ acoustic; → wave; → equation. algebraic equation   هموگش ِ جبری   hamugeš-e jabriFr.: équation algébrique   An equation in the form of P = 0, where P is a → polynomial having a finite number of terms.→ algebra; → equation. annual equation   هموگش ِ سالانه   hamugeš-e sâlânéFr.: équation annuelle   An irregularity in the Moon's orbit, which can amount to 11 degrees in a period of one year. It results from the Sun's disturbing effect on the motion of the Moon due to varying distance between them.→ annual; → equation. Antoine equation   هموگش ِ آنتوان   hamugeš-e AntoineFr.: équation d'Antoine   A mathematical expression, derived from the → Clausius-Clapeyron equation, of the relation between the vapor pressure and the temperature of pure substances. It shows that the logarithm of vapor pressure is linearly dependent on the reciprocal of → absolute temperature.Named after Louis Charles Antoine (1825-?), a French marine engineer, who derived the equation; → equation. Arrhenius equation   هموگش ِ آرنیوس   hamugeš-e ArrheniusFr.: équation d'Arrhenius   An important relationship in physical chemistry that combines the concepts of → activation energy and the → Maxwell-Boltzmann distribution law. It is expressed by: k = Ae-Ea/(RT), where k is the chemical → reaction rate, Ea is the activation energy, R is the → gas constant, and T is → temperature.Named for Svante Arrhenius (1859-1927), Swedish chemist and physicist who suggested the relationship in 1889. Bernoulli equation   هموگش ِ برنویی   hamugeš-e BernoulliFr.: équation de Bernoulli   The equation expressing → Bernoulli's theorem: P + (1/2)ρV2 + ρgz = constant, where P is the fluid → pressure, V is → velocity, ρ is → density, g is the acceleration due to → gravity, and z is the vertical reference → level. The theree terms are called → static pressure, → dynamic pressure, and → hydrostatic pressure, respectively. The Bernoulli equation states that the total pressure along a → streamline is → constant. Bessel equation   هموگش ِ بسل   hamugeš-e BeselFr.: équation de Bessel   A linear second-order differential equation, the solutions to which are called Bessel functions.From → Bessel; → equationHamugeš, → equation. Boltzmann's equation   هموگش ِ بولتسمن   hamugeš-e BoltzmannFr.: équation de Boltzmann   1) An equation that expresses the relative number (per unit volume) of → excited atoms in different states as a function of the temperature for a gas in → thermal equilibrium: Nu/Nl = (gu/gl) exp (-ΔE/kTex), where Nu and Nl are the upper level and lower level populations respectively, gu and gl the → statistical weights, ΔE = hν the energy difference between the states, k is → Boltzmann's constant, and h  → Planck's constant. canonical equation   هموگشِ هنجاروار   hamugeš-e hanjârvârFr.: équation canonique   The most general form of an equation.→ canonical; → equation. Cauchy's equation   هموگش ِ کوشی   hamugeš-e CauchyFr.: équation de Cauchy   A relationship between the → refractive index (n) and the wavelength of light (λ) passing through a medium. It is commonly stated in the following form: n = A + B/λ2 + C/λ4, where A, B, and C are constants characterizing the medium. The two-component Cauchy equation is n = A + B/λ2, from which the dispersion becomes dn/dλ = -2B/λ3 showing that dispersion varies approximately as the inverse cube of the wavelength. The dispersion at 4000 A will be about 8 times as large as at 8000 Å.Named after Augustin Louis Cauchy (1789-1857), French mathematician and physicist who found the first equation of dispersion in 1836; → equation. characteristic equation   هموگش ِ سرشتاری   hamugeš-e sereštâriFr.: équation caractéristique   Physics: An analytical relationship between a set of physical variables that determines the state of a physical system. Math.: The equation which is solved to find a matrix's eigenvalues, also called the characteristic polynomial. chemical equation   هموگش ِ شیمیایی   hamugeš-e šimiyâyiFr.: équation chimique   The symbolic representation of a chemical reaction where the formulae of the → reactants are placed on the left and the formulae of → products on the right of an arrow.→ chemical; → equation. Clapeyron equation   هموگش ِ کلاپرون   hamugeš-e ClapeyronFr.: équation de Clapeyron   An equation that relates the temperature and pressure dependence of phases in equilibrium with the heat interaction and volume change associated with a phase change: dP/dT = L/T ΔV, where dP/dT is the slope of the coexistence curve, L is the → latent heat, T is the temperature, and ΔV is the volume change of the phase transition.Named after Émile Clapeyron (1799-1864), a French engineer and physicist, one of the founders of → thermodynamics; → equation. Clausius equation   هموگش ِ کلاؤزیوس   hamugeš-e ClausiusFr.: équation de Clausius   A first-order improvement on the → ideal gas law that corrects for the finite volume of molecules. After Rudolf Clausius (1822-1888), a German physicist and mathematician, → equation. Clausius-Clapeyron equation   هموگش ِ کلاؤزیوس-کلاپرون   hamugeš-e Clausius-ClapeyronFr.: équation de Clausius-Clapeyron   An approximation of the → Clapeyron equation for liquid-vapor equilibrium that incorporates the → ideal gas law and states that the logarithm of vapor pressure is inversely proportional to temperature. Compton equation   هموگشِ کامپتون   hamugeš-e ComptonFr.: équation de Compton   Theoretical equation which gives the change in the photon wavelength due to the → Compton effect.→ Compton; → equation. cosmic energy equation   هموگش ِ کاروژ ِ کیهانی   hamugeš-e kâruž-e keyhâniFr.: équation de l'énergie cosmique   Same as the → Layzer-Irvine equation.→ cosmic; → energy; → equation. cubic equation   هموگش ِ کابی   hamugeš-e kâbiFr.: équation cubique   An equation containing unknowns of the third power; the general form: ax3 + bx2 + cx + d = 0.Cubic, of or pertaining to → cube; → equation. de Broglie equation   هموگش ِ دوبروی   hamugeš-e de BroglieFr.: équation de de Broglie   According to the → de Broglie hypothesis, which has been verified by experiments, every → particle of matter, whatever its nature, has a characteristic → wavelength associated with its wavelike quantum aspect. The de Broglie equation gives the equivalent wavelength of a moving particle: λ = h/mv, where h is → Planck's constant, m the mass of the particle, and v its velocity. See also: → de Broglie wavelength, → Davisson-Germer experiment.Named after Louis Victor de Broglie (1892-1987), French physicist, creator of a new field in physics, wave mechanics, who won the Nobel prize in physics in 1929. → equation Dieterici equation   هموگش ِ دیتریسی   hamugeš-e DietericiFr.: équation de Dieterici   An → equation of state for → real gases which leads to the → van der Waals equation as a → first approximation. It is of the form P(V - b) [exp (a/VRT)] = RT, where P is the pressure, V is the volume, T is the thermodynamic temperature, R is the → gas constant, and a and b are the constants characteristic of the gas.Named after Conrad Dieterici (1858-1929), a German physicist; → equation.

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