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: 12 Search : beam
beam
  تابه   
tâbé (#)

Fr.: 1) faisceau, 2) lobe, 3) tache de diffraction   

1) A collection of nearly parallel → light  → rays or a concentrated stream of → particles. See also → beam of light.
2) The area of the sky being observed at any one time by a → radio telescope.
3) The size of the → diffraction pattern; synonymous with point spread function.

M.E. beem, from O.E. beam "tree;" akin to O.H.G boum "tree," Ger. Baum.

Tâbé, from tâb; tâbidan "light; to shine" + noun suffix.

beam efficiency
  کار‌آیی ِ تابه   
kârâi-ye tâbé

Fr.: efficacité de lobe   

A parameter indicating the quality of an antenna as a direction measuring device. It is given by the ratio of the total received power contained in the main beam of an antenna to the total power (including the sidelobes); the same as main beam efficiency. See also → beamwidth.

beam; → efficiency.

beam of light
  تابه‌ی ِ نور   
tâbe-ye nur (#)

Fr.: faisceau lumineux   

A relatively large bundle of → rays of light. See also → pencil of light.

beam; → light.

beam of particles
  تابه‌ی ِ ذره   
tâbe-ye zarré

Fr.: faisceau de particules   

A narrow unidirectional flow of particles

beam; → particle.

beam splitter
  فاقگر ِ تابه   
fâqgar-e tâbé

Fr.: lame séparatrice   

A partially reflecting mirror which permits a part of the light beam to pass through and reflects the rest.

beam; splitter, from to split, from M.Du. splitten, from P.Gmc. *spl(e)it-, PIE *(s)plei- "to split, splice."

Fâqgar, from fâq "split, breach, division" + tâbébeam.

beam switching
  دگربانی ِ تابه   
degarbâni-ye tâbé

Fr.: permutation de lobe   

In single dish radio astronomy, any technique which forms the difference of signals received from two (or more) pointings on the sky without physically moving the main reflector of the antenna. By rapidly forming differences between sky positions that do and do not contain astronomical sources, beam switching can minimize the corruption of spectral baselines by non-idealities in the instrumental frequency response, or of continuum observations by atmospheric fluctuations.

beam; → switching.

beamwidth
  تابه-پهنا   
tâbe-pahnâ

Fr.: largeur de lobe   

The angle between the two directions in the main beam at which the power response has fallen to half its maximum value. → beam efficiency.

From → beam + → width.

Tâbe-pahnâ, from tâbé, → beam, + pahnâ "width," → broad.

colliding-beam accelerator
  شتابگر با تابه‌ی ِ همکوبنده   
šetâbgar bâ tâbe-ye hamkubandé

Fr.: accélérateur à faisceau de collision   

Same as → collider.

collide; → beam; → accelerator.

collimated beam
  تابه‌ی ِ همراستا   
tâbe-ye hamrâstâ

Fr.: faisceau collimaté   

A → beam of → photons or → subatomic particles with a narrow → cross section that has little or no spatial spread.

collimated; → beam.

half-power beamwidth (HPBW)
  پهنای ِ تابه در نیم‌توان   
pahnâ-ye tâbé dar nim-tavân

Fr.: largeur à mi-hauteur   

The angle between extreme points of the main lobe of an antenna pattern where the sensitivity of the antenna is half the value at the center of the lobe. This is the nominal resolving power of the antenna system.

half; → power; → beam; → width.

main beam
  لپ ِ فریست   
lap-e farist

Fr.: lobe principal   

Same as → main lobe.

main; → beam.

pencil beam
  تابه‌ی ِ باریک   
tâbe-ye bârik

Fr.: faisceau étroit   

A beam of radiant energy in the form of a narrow cone or cylinder.

pencil; → beam.