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.
M.E. beem, from O.E. beam "tree;" akin to O.H.G boum "tree," Ger. Baum.
Tâbé, from tâb; tâbidan "light; to shine" + -é noun suffix.
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
tâbe-ye nur (#)
Fr.: faisceau lumineux
A relatively large bundle of → rays of light. See also → pencil of light.
beam of particles
Fr.: faisceau de particules
A narrow unidirectional flow of particles
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" + tâbé→ beam.
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.
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.
šetâbgar bâ tâbe-ye hamkubandé
Fr.: accélérateur à faisceau de collision
Same as → collider.
→ collide; → beam; → accelerator.
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)
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.
Fr.: lobe principal
Same as → main lobe.
Fr.: faisceau étroit
A beam of radiant energy in the form of a narrow cone or cylinder.