Fr.: fonction de Planck
Same as → Planck's blackbody formula.
derâzâ-ye Planck (#)
Fr.: longueur de Planck
The size limit, lP = √ (ħ G/ c3), about 10-33 cm, at which Einstein's notions of space-time are supposed to break down, and space is predicted to become "foam like."
Fr.: masse de Planck
The unit of mass in Planck's system of physical units, mP = √ (ħ c/ G) = 2.176 x 10-8 kg. It is also the mass of a black hole whose Compton wavelength is comparable to its Schwarzschild radius.
Fr.: postulat de Planck
The postulate that the energy of oscillators in a blackbody is quantized by E = nhν, where n = 1, 2, 3, ..., h is Planck's constant, and ν the frequency.
Fr.: Satellite Planck
A European Space Agency (ESA) mission to map the full sky in the 30 GHz to 1 THz range and to measure the → anisotropies of the → cosmic microwave background (CMB) with a sensitivity set by fundamental limits, i.e. photon noise and contamination by foregrounds. It was launched on 14 May 2009, together with the → Herschel Satellite. Its observing position is a halo orbit around the L2 → Lagrangian point, some 1.5 million km from Earth. Its → Gregorian-like off-axis telescope has an effective aperture of 1.5 m and images the sky on two sets of feed-horns. The Low Frequency Instrument (LFI, at frequencies 30, 44, 70 GHz) amplifies with High Electron Mobility Transistors cooled at 20 K the radiation collected by 13 horns. The High Frequency Instrument (HFI, at 100, 143, 217, 353, 545, 857 GHz) detects the shorter waves with 52 bolometers cooled at only 0.1 degree above the → absolute zero. Both instruments can detect both the total intensity and polarization of photons. The Planck mission is intended to provide maps with a sensitivity of a few micro-Kelvin and an angular resolution down to 5 arcmin, which is considered as a major improvement with respect to the Wilkinson Microwave Anisotropy Probe (→ WMAP) launched by the NASA in 2002. Planck will provide a major source of information relevant to several cosmological and astrophysical issues, such as testing theories of the early Universe and the origin of cosmic structure. It will also provide to astronomers 9 complete maps of the full sky at wavelengths from 0.3 mm to 1 cm, that complement the 4 maps taken by the → IRAS satellite in the 2.5 to 100 micrometer range.
Fr.: échelle de Plancck
Fr.: spectrum de Planck
Same as → blackbody spectrum.
Fr.: temps de Planck
The time representing the → Planck length divided by the → speed of light. It is expressed by: tP = (Għ/c5)1/2≅ 5.4 x 10-44 s, where G is the → gravitational constant, ħ is the → reduced Planck's constant, and c is the → speed of light. At the Planck time, the mass density of the Universe is thought to approach the → Planck density.
yekâhâ-ye Planck (#)
Fr.: unités de Planck
A set of → natural units in which the normalized units are: the gravitational constant, Planck's constant, the speed of light, the Coulomb constant, and Boltzmann's constant.
Planck's blackbody formula
disul-e siyah jesm-e Planck
Fr.: formule du corps noir de Planck
A formula that determines the distribution of intensity of radiation that prevails under conditions of thermal equilibrium at a temperature T: Bv = (2hν3 / c2)[exp(hν / kT) - 1]-1 where h is Planck's constant and ν is the frequency.
pâyâ-ye Planck (#)
Fr.: constante de Planck
Planck's radiation law
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.
1) hâmon (#); 2) taxt (#)
1) (n.) a flat or level surface.
1) From L. plantum "flat surface," noun use of adj. planus "flat,
1) Hâmon, variant of hâmun "plain, level ground;" Mid.Pers. hâmôn
"level, flat;" Proto-Iranian *hāma-van-,
*hāma- "same, equally, even; together, with" (Mod.Pers./Mid.Pers.
ham-; cf. Skt. sam-; also O.Pers./Av. hama-
"one and the same;" Skt. sama-; Gk. homos-;
originally identical with PIE numeral *sam-
"one," from *som-. The Av. ham- appears in various forms:
han- (before gutturals, palatals, dentals) and also hem-,
hen-) + *-van- suffix.
šekl-e hâmon, ~ taxt
Fr.: figure plane
A two-dimensional geometric figure. The points of the figure lie entirely in a plane.
âyene-ye taxt (#)
Fr.: miroir plan
A mirror whose reflective surface is neither concave nor convex.
plane of polarization
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 of rotation
Fr.: plan de rotation
plane of the sky
Fr.: plan du ciel
An imaginary plane that is perpendicular to the → line of sight.
plane of vibration
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.
Fr.: polarisation plane
Same as → linear polarization.