tâbeš-e paszaminé, ~ zaminé
Fr.: rayonnement du fond
tâbeš-e siyah-jesm (#)
Fr.: rayonnement de corps noir
tâbeš-e Čerenkov (#)
rayonnement de Čerenkov
Visible radiation emitted when → charged particles pass through a transparent medium faster than the speed of light in that medium.
Named after Pavel A. Čerenkov (1904-1990), Russian physicist, who discovered the phenomenon. He shared the Nobel prize 1958 in physics with Ilya Frank and Igor Tamm, who in 1937 gave the theoretical explanation for this radiation.
Fr.: rayonnement corpusculaire
A stream of atomic or subatomic particles.
cosmic background radiation
tâbeš-e paszaminé-ye keyhâni
Fr.: rayonnement du fond cosmique
cosmic microwave background radiation (CMBR)
tâbeš-e rizmowj-e paszaminé-ye keyhâni
Fr.: rayonnement du fond cosmique microonde
The diffuse → electromagnetic radiation in the → microwave band, coming from all directions in the sky, which consists of relic photons left over from the very hot, early phase of the → Big Bang. More specifically, the CMBR belong to the → recombination era, when the → Universe was about 380,000 years old and had a temperature of about 3,000 K, or a → redshift of about 1,100. The photons that last scattered at this epoch have now cooled down to a temperature of 2.73 K. They have a pure → blackbody spectrum as they were at → thermal equilibrium before → decoupling. The CMB was discovered serendipitously in 1965 by Penzias and Wilson (ApJ L 142, 419) and was immediately interpreted as a relic radiation of the Big Bang by Dicke et al. (1965, ApJL 142, 383). Such a radiation had been predicted before by Gamow (1948, Nature 162, 680) and by Alpher and Herman (1948, Nature 162, 774). This discovery was a major argument in favor of the Big Bang theory. In 1992, the satellite → Cosmic Background Explorer (COBE) discovered the first anisotropies in the temperature of the CMB with an amplitude of about 30 µK. See also: → cosmic microwave background anisotropy, → dipole anisotropy, → CMB lensing, → CMB angular power spectrum, → acoustic peak, → baryon acoustic oscillation, → WMAP.
Fr.: rayonnement dipolaire
Fr.: rayonnement électromagnétique
Radiation propagating in the form of an advancing wave in electric and magnetic fields. It includes radio waves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
tâbeš-e gerâneši (#)
Fr.: rayonnement gravitationnel
tâbeš-e Hawking (#)
Fr.: rayonnement de Hawking
The radiation produced by a → black hole when → quantum mechanical effects are taken into account. According to quantum physics, large fluctuations in the → vacuum energy occurs for brief moments of time. Thereby virtual particle-antiparticle pairs are created from vacuum and annihilated. If → pair production happens just outside the event horizon of a black hole, as soon as these particles are formed they would both experience drastically different → gravitational attractions due to the sharp gradient of force close to the black hole. One particle will accelerate toward the black hole and its partner will escape into space. The black hole used some of its → gravitational energy to produce these two particles, so it loses some of its mass if a particle escapes. This gradual loss of mass over time means the black hole eventually evaporates out of existence. See also → Bekenstein formula, → Hawking temperature.
Named after the British physicist Stephen Hawking (1942-2018), who provided the theoretical argument for the existence of the radiation in 1974; → radiation.
tâbeš-e forusorx (#)
Fr.: rayonnement infrarouge
That part of the → electromagnetic radiation lying beyond the red, between the radio and the visible regions of the → electromagnetic spectrum. The wavelengths range from about 0.8 → microns (μm) to about 1000 μm. See also: → near-infrared; → mid-infrared; → far-infrared; → submillimeter radiation.
intensity of radiation
Fr.: intensité de rayonnement
The rate of emitted energy from unit surface area through unit solid angle. The radiation from a surface has different intensities in different directions.
interstellar radiation field
meydân-e tâbeš andaraxtari
Fr.: champ de rayonnement interstellaire
A global ionizing radiation in the → interstellar medium provided by various sources all together.
tâbeš-e yonandé (#)
Fr.: rayonnement ionisant
A photon that has enough energy to remove an electron from an atom or molecule, thus producing an ion and free electrons.
1) tâbešdehi, tâbešgiri; 2) nurgostard
1) Exposure to any kind of radiation or atomic particles.
1) Tâbešdehi, tâbešgiri;, from tâbeš→ radiation + giri verbal noun of gereftan
"to take, seize" (Mid.Pers. griftan, Av./O.Pers. grab- "to take, seize," cf.
Skt. grah-, grabh- "to seize, take," graha
"seizing, holding, perceiving," M.L.G. grabben "to grab,"
from P.Gmc. *grab, E. grab "to take or grasp suddenly;"
PIE base *ghrebh- "to seize"); dahi verbal noun of dâdan
"to give," Mid.Pers. dâdan "to give" (O.Pers./Av. dā- "to give, grant, yield,"
dadāiti "he gives;" Skt. dadáti "he gives;"
Gk. tithenai "to place, put, set," didomi "I give;"
L. dare "to give, offer," facere "to do, to make;"
Rus. delat' "to do;" O.H.G. tuon, Ger. tun,
O.E. don "to do;" PIE base *dhe- "to put, to do").
tâbeš-e doqotbe-ye meqnâtisi (#)
Fr.: rayonnement du dipôle magnétique
Radiation emitted by a rotating magnet.
microwave background radiation
tâbeš-e paszamine-ye rizmowj
Fr.: rayonnement micro-onde du fond cosmique
Thermal radiation with a temperature of 2.73 K that is apparently uniformly distributed in the Universe. It is believed to be a redshifted remnant of the hot radiation that was in thermal equilibrium with matter during the first hundred thousand years after the Big Bang. Same as → cosmic microwave background (CMB) radiation.
tâbeš-e rizmowj (#)
Fr.: rayonnement micro-onde
Electromagnetic radiation carried by → microwaves.
tâbeš-e nâhamdus (#)
Fr.: rayonnement incohrént
Radiation having waves that are out of phase in space and/or time; radiation which is not → coherent.
tâbeš-e nâgarmâyi (#)
Fr.: rayonnement non thermique
The electromagnetic radiation whose characteristics do not depend on the temperature of the emitting source. In contrast to → thermal radiation, it has a different spectrum from that of → blackbody radiation. The three common types of non-thermal radiation in astronomy are: → synchrotron radiation, → bremsstrahlung radiation, and → maser → stimulated emission.