Fr.: continuum de Balmer
A continuous range of wavelengths in the Balmer spectrum of
hydrogen corresponding to transitions between the energy levels
Fr.: décrément de Balmer
The intensity ratio among the couple of relatively adjacent → Balmer lines, for example Hα/Hβ and Hβ/Hγ, which have well-known theoretical values. They are used to determine the → interstellar extinction.
Fr.: discontinuité de Balmer
An abrupt decrease in the intensity of the continuum at the limit of the → Balmer series of hydrogen (at about 3650 Å), caused by the energy absorbed when electrons originally in the second → energy level are ionized. Same as → Balmer jump.
Fr.: formule de Balmer
A special solution of the mathematical formula which represents
the wavelengths of the various spectral series of hydrogen in which the
lower energy level is n =
Fr.: saut de Balmer
Same as → Balmer discontinuity.
Fr.: limite de Balmer
Fr.: raies de Balmer
seri-ye Bâlmer (#)
Fr.: série de Balmer
A series of hydrogen → spectral lines
(Hα, Hβ, Hγ, and others) that lies in the visible
portion of the spectrum and results when electrons from upper
→ energy levels (n > 2) undergo
→ transition to n =
General:1) A strip serving to encircle
and bind one object or to hold a number of objects together.
2) A strip or stripe that contrasts with something else in color,
texture, or material.
From M.E. bende, O.E. bend, from O.Fr. bande, bende, P.Gmc. *bindan, from PIE *bendh- "to bind" (cf. Goth bandi "that which binds;" Av./O.Pers. band- "to bind, fetter," banda- "band, tie," Skt. bandh- "to bind, tie, fasten," bandhah "a tying, bandage."
Bând, adoption from E. band, which is cognate and synonymous with Pers. band, present tense stem of bastan "to bind, shut," Mid.Pers. bastan, band, Av./O.Pers. band-, as explained above. See also → strip.
bândsar, sar-e bând
Fr.: tête de bande
A location on the spectrogram of a molecule at which the lines of a band stack.
Band head, from → band + head, from O.E. heafod "top of the body," also "upper end of a slope," also "chief person, leader," from P.Gmc. *khaubuthan, from PIE *kauput- "head" (cf. Skt. kaput-, L. caput "head," Lori kapu "head," kapulek "skull, middle of the head").
Bândsar, from → bând + sar "head," soru, sorun "horn," karnâ "a trumpet-like wind instrument" (originally made from animal horns), variant sornâ "a wind instrument;" Mid.Pers. sar "head," sru "horn;" Av. sarah- "head," srū- "horn, nail;" cf. Skt. śiras- "head, chief;" Gk. kara "head," karena "head, top," keras "horn;" L. cornu "horn," cerebrum "brain;" P.Gmc. *khurnaz (E. horn; Ger. Horn, Du. horen), from PIE *ker- "head, horn."
Fr.: spectre de bande
A spectrum which consists of a number of bands each having one sharp edge. Each band is composed of a large number of closely spaced emission or absorption lines. Band spectra are typical of molecules. Bands produced by titanium oxide, zirconium oxide, and carbon compounds are characteristic of low temperature stars.
Fr.: bande passante
A range of frequencies that can pass through a filter such as one in an electrical circuit.
From → band + pass, from O.Fr. passer, from V.L. *passare "to step, walk, pass," from L. passus "step, pace;" cf. Pers. pâ "foot," pey "step."
Gozar-bând, from gozar "passage, transit, passing," gozaštan "to pass, cross, transit," from Mid.Pers. vitârtan + bând, → band.
Fr.: filtre de bande
An electric filter that transmits a known band of frequencies but suppresses unwanted frequencies above and below this band.
Fr.: largeur de bande
The portion of the electromagnetic spectrum that is permitted to pass through an electronic device, such as a radio telescope detector. The term refers to either a wavelength interval or a frequency interval.
1) bâr (#); 2) milé (#)
Fr.: 1) bar; 2) barre
1) A unit of → pressure, not belonging to the
→ International System (SI),
equivalent to 106→ dynes
per cm2 and 0.987 → atmospheres.
1) From Gk. baros "weight," cf. Skt guru, L. gravis;
PIE *gwere- "heavy;" cf.
Pers. bâr "weight," gerân "heavy,"
L. brutus "heavy, dull, stupid, brutish,"
Skt. bhara- "burden, load," bharati "he carries;"
PIE *bher- "carry, give birth."
1) Loan from Fr., as above.
A whitish, malleable, metallic → chemical element; symbol Ba. → Atomic number 56; → atomic weight 137.33; → melting point 725°C; → boiling point 1,640°C; → specific gravity 3.5 at 20°C. Barium was discovered by the Swedish pharmacist and chemist Carl Wilhelm Scheele in 1774. It was first isolated by the British chemist Humphry Davy in 1808.
From Mod.L., from Gk. barys "heavy," from the mineral barytes "heavy spar" (BaSO4), in which the element was discovered; cognate with Pers. bâr "weight," → bar.
Fr.: étoile à barium
adasi-ye Barlow (#)
Fr.: lentille de Barlow
A → negative lens placed in a telescope between the → objective and the → ocular. Its diverging action reduces the convergence of the light cone, forming a larger image at a slightly greater distance.
Peter Barlow (1776-1862), English physicist; → lens.
In nuclear physics, unit of area for measuring the cross-sections of nuclei. 1 barn equals 10-24 sq. cm.
Barn, from O.E. bereærn "barn," lit. "barley house," from bere "barley" + aern "house." The use of barn in nuclear physics comes from the fact that the term denotes also "an unexpectedly large quantity of something." It seems that when physicists were first studying nuclear interactions, they found out that the interaction probabilities, or cross-sections, were far more larger than expected; the nuclei were `as big as a barn'.
From Edward Emerson Barnard (1857-1923) American astronomer who made several obserational discoveries.