An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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place-value notation
  نمادگان ِ جا-ارزشی   
nemâdgân-e jâ-arezeši

Fr.: notation positionnelle   

A mathematical notation system in which the → numerals get different values depending on their position relative to the other numerals. Same as → positional notation and → positional number system.

place; → value; → notation.

Planck constant
  پایای ِ پلانک   
pâyâ-ye Planck (#)

Fr.: constante de Planck   

A physical constant that determines the energy of quantum as a function of its frequency; symbol h. Also called → Planck's constant. On 16 November 2018, the International Bureau of Weights and Measures (BIPM) voted to redefine the kilogram by fixing the value of the Planck constant, thereby defining the kilogram in terms of the second and the speed of light. Starting 20 May 2019, the new value is exactly 6.626 070 15 × 10-34 J s. The → reduced Planck constant, ħ = h / 2π, is also called the → Dirac constant.

Planck; → constant.

Planck distribution
  واباژش ِ پلانک   
vâbâžeš-e Planck

Fr.: distribution de Planck   

The distribution of radiation with wavelength for a blackbody, given by → Planck's radiation law.

Planck; → distribution.

Planck function
  کریای ِ پلانک   
karyâ-ye Planck

Fr.: fonction de Planck   

Same as → Planck's blackbody formula.

Planck; → function.

Planck's constant
  پایای ِ پلانک   
pâyâ-ye Planck (#)

Fr.: constante de Planck   

Planck constant.

Planck; → constant.

Planck's radiation law
  قانون ِ تابش ِ پلانک   
qânun-e tâbeš-e Planck

Fr.: loi du rayonnement de Planck   

An equation that expresses the energy radiated per unit area per unit time per unit wavelength range by a blackbody as a function of temperature. It is expressed by → Planck's blackbody formula.

Planck; → radiation; → law.

plane of polarization
  هامن ِ قطبش   
hâmon-e qotbeš

Fr.: plan de polarisation   

In a → linearly polarized light, a plane perpendicular to the → plane of vibration and containing the direction of propagation of light. It is also the plane containing the direction of propagation and the magnetic vector (H) of the electromagnetic light wave.

plane; → polarization.

plane of rotation
  هامن ِ چرخش   
hâmon-e carxeš

Fr.: plan de rotation   

For a rotating object, the plane → perpendicular to the → rotation axis.

plane; → rotation.

plane of vibration
  هامن ِ شیوش   
hâmon-e šiveš

Fr.: plan de vibration   

In a → linearly polarized light, a plane perpendicular to the → plane of polarization and containing the direction of propagation of light. It is also the plane containing the direction of propagation and the electric vector (E) of the electromagnetic light wave.

plane; → polarization.

plane polarization
  قطبش ِ هامنی   
qotbeš-e hâmoni

Fr.: polarisation plane   

Same as → linear polarization.

plane; → polarization.

planetary aberration
  بیراهش ِ سیاره‌ای   
birâheš-e sayyâreyi

Fr.: aberration planétaire   

The difference between the true position of a planet and its apparent position, due to the time required for light to travel the distance from the planet to Earth. Correction for planetary aberration is necessary in determining orbits.

planetary; → aberration.

planetary precession
  پیشایان ِ سیاره‌ای   
pišâyân-e sayyâre-yi

Fr.: précession planétaire   

The motion of the → ecliptic plane caused by the gravitational influence of the other planets, mainly → Jupiter. The observational effect of planetary precession is similar to that of the → lunisolar precession. But planetary precession causes the → equinoxes to move along the ecliptic in the opposition direction (eastward) from that of luni-solar precession (westward) and at a much slower rate: 0''.12 per year. Same as → precession of ecliptic.

planetary; → precession.

PLAnetary Transits and Oscillations of stars (PLATO)
  پلاتو   
PLATO

Fr.: PLATO   

A space observatory under development by the → European Space Agency for launch around 2024. Its objective is to detect and characterize → exoplanets by means of their → transit signature in front of a very large sample of → bright stars, and measure the seismic oscillations (→ asteroseismology) of the parent stars orbited by these planets in order to understand the properties of the exoplanetary systems.

planetary; → transit; → oscillation; → star.

plano-concave lens
  عدسی ِ تخت-کاو   
adasi-ye taxt-kâv (#)

Fr.: lentille plano-concave   

A → divergent lens composed of one concave surface and one plane surface. This type of lens has a negative focal point and produces a → virtual image.

plano-; → concave; → lens.

plano-convex lens
  عدسی ِ تخت-کوژ   
adasi-ye taxt-kuž (#)

Fr.: lentille plano-convexe   

A → convergent lens that has one flat side and one convex side. Plano-convex lenses focus parallel rays of light to a positive point, thus forming → real images.

plano-; → convex; → lens.

plasma oscillation
  نوِش ِ پلاسما   
naveš-e plâsmâ

Fr.: oscillation de plasma   

The oscillatory motion of electrons in a neutral plasma around their equilibrium position while the ions remain at rest. When electrons are displaced by any kind of perturbation with respect to ions, a pair of positive and negative charged regions is formed. The Coulomb force accelerates back the displaced electrons, which get kinetic energy. The electrons overshoot their original positions by the same amount as their first displacement.

plasma; → oscillation.

plasmon
  پلاسمون   
plâsmon

Fr.: plasmon   

Physics: The quasiparticle resulting from the → quantization of → plasma oscillations. Plasmons are collective oscillations of free electrons inside or on surfaces of materials.

From plasm-, from → plasma + → -on.

plasmonics
  پلاسمونیک   
plâsmonik

Fr.: plasmonique   

The research area dealing with the interaction of → plasmons and → photons and the technology of its practical use. Plasmonics represents one of the most active research fields at the interface of → nanotechnology and → optics.

plasmon; → -ics.

plastic deformation
  وادیسش ِ شوکایند   
vâdiseš-e šukâyand

Fr.: déformation plastique   

Permanent → deformation of a → solid subjected to a → stress.

plastic; → deformation.

plate tectonics
  سازانیک ِ پلاک   
sâzânik-e pelâk

Fr.: tectonique des plaques   

The theory supported by a wide range of evidence in which the Earth's crust is composed of several large, thin, relatively rigid plates that move relative to one another. The interaction of the plates at their boundaries causes seismic and tectonic activity along these boundaries. See also → continental drift.

plate; → tectonics.

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