An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



Number of Results: 18 Search : polarization
B-mode polarization
  قطبش ِ ترز ِ B   
qotbeš-e tarz-e B

Fr.: polarisation en mode B   

A → polarization component in the → cosmic microwave background radiation that depends only on → curl, is independent of → gradient, and has → handedness that distinguishes left from right. The B-mode is due to only → vector perturbations or → tensor perturbations. It has two types, the first type, which constitutes the majority of the B-mode polarization, results from → lensing by galaxies that twist the → E-mode polarized light on its journey from the other side of the → observable Universe. The second type can be produced only by → gravitational waves, not by density perturbations. This type of B-mode is incredibly faint, producing temperature variations of about 0.4 microK and accounting for just one part in 10 million in the CMB temperature distribution. It is expected to be generated during cosmic → inflation shortly after the → Big Bang. The → BICEP2 team announced in March 2014 that they had detected the second type of B-modes, consistent with inflation and gravitational waves in the → early Universe. The detected degree scale B-mode polarization has a tensor-to-scalar ratio, r = 0.2 (+0.07, -0.05), which is a measure of the amplitude of the primordial gravitational waves.

B, indicating magnetic-field like; → mode; → polarization.

circular polarization
  قطبش ِ پرهونی، ~ دایره‌ای   
qotbeš-e parhuni, ~ dâyereyi (#)

Fr.: polarisation circulaire   

The → polarization of an → electromagnetic radiation in which the electric field vector describes a circle about the direction of propagation at any point in the path of the radiation. Circular polarization is a combination of two perpendicular → linearly polarized waves that are 90 degrees out of phase with each other. Circular polarization may be referred to as "right-hand" or "left-hand," depending on the rotation direction as viewed by the observer.

circular; → polarization.

cosmic microwave background polarization
  قطبش ِ زمینه‌ی ِ ریزموج ِ کیهانی   
qotbeš-e zamine-ye rizmowj-e keyhâni

Fr.: polarisation du rayonnement du fond cosmique microonde   

The polarization of the → cosmic microwave background radiation due to → Thomson scattering by → free electrons during the → recombination era. The polarization can greatly enhance the precision with which the parameters associated with → acoustic oscillations are derived; because it carries directional information on the sky. When an → electromagnetic wave is incident on a free electron, the scattered wave is polarized perpendicular to the incidence direction. If the incident radiation were → isotropic or had only a → dipole variation, the scattered radiation would have no net polarization. However, if the incident radiation from perpendicular directions (separated by 90°) had different intensities, a net → linear polarization would result. Such → anisotropy is called → quadrupole because the poles of anisotropy are 360°/4 = 90° apart.

cosmic; → microwave; → background; → polarization.

degree of polarization
  درجه‌ی ِ قطبش   
daraje-ye qotbeš

Fr.: degré de polarisation   

The ratio of the intensity of polarized portion of light to the total intensity at a point in the beam.

degree; → polarization.

vâqotbeš (#)

Fr.: dépolarisation   

Reducing or randomizing the polarization of an electromagnetic wave, by transmission through a non-homogeneous medium or a depolarizer.

from → de- + → polarization.

E-mode polarization
  قطبش ِ ترز ِ E   
qotbeš-e tarz-e E

Fr.: polarisation en mode E   

A → polarization component in the → cosmic microwave background radiation that depends only on → gradient, is independent of → curl and does not have → handedness. In contrast to the → B-mode, the E-mode may be due to both the → scalar perturbations and → tensor perturbations.

E, indicating electric-field like; → mode; → polarization.

elliptical polarization
  قطبش ِ بیضی‌گون   
qotbeš-e beyzigub

Fr.: polarization elliptique   

The → polarization of an → electromagnetic radiation in which the electric vector at any point in the path of the beam describes an ellipse in a plane perpendicular to the propagation direction. Elliptical polarization results from the combination of two perpendicular → linearly polarized waves whose → phase difference is other than 0, 90, or 180°. The form of the ellipse is determined by the amplitudes of the component waves and the phase difference. → Linear polarization and → circular polarization can be considered as limiting cases of elliptical polarization.

elliptical; → polarization.

interstellar polarization
  قطبش ِ اندر-اختری   
qotbeš-e andaraxtari

Fr.: polarisation interstellaire   

The polarization of starlight caused by aligned → interstellar grains, so that initially → unpolarized light from a star is partially polarized by the time it reaches the Earth.

interstellar; → polarization.

linear polarization
  قطبش ِ خطی   
qotbeš-e xatti (#)

Fr.: polarisation linéaire   

Of an electromagnetic radiation, a → polarization in which the electric vibrations are confined to one plane along the direction of propagation. Also called → plane polarization. See also → circular polarization.

linear; → polarization.

negative polarization
  قطبش ِ ناییدار   
qotbeš-e nâyidâr

Fr.: polarisation négative   

A type of polarization in which the direction of polarization becomes reversed.

negative; → polarization.

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 polarization
  قطبش ِ هامنی   
qotbeš-e hâmoni

Fr.: polarisation plane   

Same as → linear polarization.

plane; → polarization.

qotbeš (#)

Fr.: polarisation   

1) Optics: A process or state in which the directions of the electric or magnetic fields of an → electromagnetic radiation change in a regular pattern. Light can be polarized by a variety of ways, involving the following processes: reflection, transmission, double refraction, and scattering. See also → unpolarized light; → linear polarization; → circular polarization; → elliptical polarization. The study of the polarization of light from astronomical sources can yield unique information in particular related to the properties of magnetic fields.
2) Electricity: A process or state in which the → dipole moments of → polar molecules in a → dielectric material get aligned under the action of an external electric field. Actually thin layers of bound charges with opposite signs appear on the surfaces of the dielectric.
3) Electricity: The accumulation of ions, produced during electrolysis, on the electrodes of a cell, increasing the resistance of the cell.

Verbal noun of → polarize.

polarization angle
  زاویه‌ی ِ قطبش   
zâviye-ye qotbeš (#)

Fr.: angle de polarisation   

Same as → polarizing angle and → Brewster angle.

polarization; → angle.

polarization charge
  بارِ قطبش   
bâr-e qotbeš


Same as → bound charge.

polarization; → charge.

polarization degree
  درجه‌ی ِ قطبش   
daraje-ye qotbeš (#)

Fr.: degré de polarisation   

degree of polarization.

polarization; → degree.

polarization fraction
  برخه‌ی ِ قطبش   
barxe-ye qotbeš

Fr.: fraction de polarisation   

The ratio expressed by P = (Ipar - Iper) / (Ipar + Iper), where Ipar and Iper are the light intensities with the electric field vector respectively parallel and perpendicular to the incident beam.

polarization; → fraction.

vacuum polarization
  قطبش ِ خلاء   
qotbeš-e xala'

Fr.: polarisation du vide   

A quantum field theory a process in which an electromagnetic field gives rise to virtual electron-positron pairs that in turn exert electromagnetic fields of their own, in a manner similar to classical dielectric polarization.

vacuum; → polarization.