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diffraction grating turi-ye parâš (#) Fr.: réseau de diffraction An optical device containing thousands of very fine parallel grooves which produce interference patterns in a way which separates out all the components of the light into a spectrum. → diffraction; → grating. |
diffraction pattern olgu-ye parâš (#) Fr.: tache de diffraction A series of concentric rings of dark and light color produced by interference. → diffraction; → pattern. Olgu, loanword from Turkish; parâš→ diffraction. |
diffraction spike sixak-e parâš Fr.: aigrette de diffraction One of several light rays emanating from a bright light source in images taken with → reflecting telescopes. They are artifacts caused by light diffracting around the support or → spider vanes of the → secondary mirror. → diffraction; → spike. |
diffraction-limited karânmand bé parâš Fr.: limité par la diffraction The quality of an → optical system that is capable of producing images with angular resolution as small as the theoretical limit of the → Airy disk. → diffraction; limited, adj. of → limit. Karânmand "bounded, limited," from karân→ boundary + -mand possession suffix; parâš→ diffraction. |
diffuse galactic light nur-e kahkašâni-ye paxšidé Fr.: lumière galactique diffuse A minor component of galactic light resulting from the diffusion of starlight by → interstellar dust near the → galactic plane. |
dilution factor karvand-e owtâleš Fr.: facteur de dilution The energy density of a radiation field divided by the equilibrium value for the same color temperature. |
double refraction šekast-e dotâyi Fr.: double réfraction Formation of two refracted rays of light from a single incident ray; property of certain crystals, notably calcite. → double; → refraction. |
doubly refracting crystal bolur-e šakst-e dotâyi Fr.: cristal à double réfraction A → transparent → crystalline substance (such as calcite, quartz, and tourmaline) that is → anisotropic relative to the → speed of light. A ray incident normally on such crystals is broken up into two rays in traversing the crystal, → ordinary ray and → extraordinary ray. → doubly; → refracting; → crystal. |
Einstein-Hilbert action žireš-e Einstein-Hilbert Fr.: action de Einstein-Hilbert In → general relativity, the → action
that yields → Einstein's field equations.
It is expressed by: → Einstein; → Hilbert space; → action. |
electron diffraction parâš-e elekroni (#) Fr.: diffraction des électrons A diffraction phenomenon resulting from the passage of electrons through matter, analogous to the diffraction of visible light. This phenomenon is the main evidence for the existence of waves associated with elementary particles; → de Broglie wavelength. → electron; → diffraction. |
electroweak interaction andaržireš-e barqânezâr Fr.: interaction électrofaible The unified description of two of the four fundamental interactions of nature, → electromagnetism and the → weak interaction which would merge into a single force under conditions of extreme temperature (above 10^{16} degrees, 10^{2} GeV) prevalent in the early history of the → Universe. → electroweak; → interaction. |
epact barafzâ Fr.: épacte 1) The time that must be added to the lunar year (12 lunations) to make it coincide
with the solar year (about 11 days). From Fr. épacte, from L. epacta, from Gk. epaktos, verbal adj. of epagein "to intercalate, add, bring forward," from epi "on" + ag-, from agein "to bring, to lead;" cf. L. agere "to drive, set in motion," → act. Barafzâ, from bar- "on, upon, up" (Mid.Pers. abar; O.Pers. upariy "above; over, upon, according to;" Av. upairi "above, over," upairi.zəma- "located above the earth;" cf. Gk. hyper- "over, above;" L. super-; O.H.G. ubir "over;" PIE base *uper "over") + afzâ, afzudan "to add, increase" (Mid.Pers. abzudan "to increase, grow;" O.Pers. abijav- "to increase, add to, promote," from abi-, aiby- "in addition to; to; against" + root jav- "to press forward;" Av. gav- "to hasten, drive;" Sk. jav- "to press forward, impel quickly, excite," javate "hastens"). |
exact razin Fr.: exact 1) Strictly accurate or correct; precise, as opposed to approximate. From L. exactus, p.p. of exigere, literally "to drive out, thrust out," also "demand, finish, measure," from → ex- "out" + agere "drive, lead, act," → act. Razin "firm, solid, strong" [Dehxodâ, Steingass], Mid.Pers. razên "firm, strong, secure, solid." |
exact differential degarsâne-ye razin Fr.: différentielle exacte If N(x,y) is a → function of two → independent variables, then dN = (∂N/∂x)dx + (∂N/∂y)dy is the exact differential. → exact; → differential. |
exact differential equation hamugeš-e degarsâneyi-ye razin Fr.: équation différentielle exacte A → differential equation composed of → continuous → differentiable functions for which certain conditions are fulfilled. The equation M(x,y)dx + N(x,y)dy = 0 is called exact if M(x,y) and N(x,y) are continuous differentiable functions for which the following relationship is fulfilled: ∂M/∂y = ∂N/∂x, and ∂M/∂y and ∂N/∂x are continuous in some region. → exact; → differential; → equation. |
exact number adad-e razin Fr.: nombre exact A value that is known with complete certainty. Examples of exact numbers are defined numbers, results of counts, certain unit conversions. Some examples: there are exactly 100 centimeters in 1 meter, a full circle is exactly 360°, and the number of students in a class can exactly be 25. |
exact science dâneš-e razin Fr.: science exacte A field of study that admits especially precise predictions and rigorous methods of testing hypotheses, especially reproducible experiments involving quantifiable predictions and measurements. |
extragalactic ostar-kahkašâni, borun-kahkašâni Fr.: extragalactique Of, pertaining to, or dealing with the space beyond the Milky Way. |
extragalactic astronomy axtaršenâi-ye ostar-kahkašâni, ~ borun-kahkašâni Fr.: astronomie extragalactique The branch of astronomy that deals with objects beyond the Milky Way, especially galaxies and quasars. → extragalactic; → astronomy. |
extragalactic background light (EBL) nur-e paszimine-ye ostarkahkeši Fr.: lumière du fond extragalactique The integrated intensity of all of the light emitted throughout the history of the Universe across the whole of the → electromagnetic spectrum, including those which are not individually detected. The EBL spectrum includes cosmological backgrounds associated with either primordial phenomena, such as the → cosmic microwave background radiation (CMBR), or photons emitted by stars, galaxies and → active galactic nuclei (AGN) due to → nucleosynthesis or other → radiative processes, including → dust scattering, → absorption and reradiation. The EBL may also contain signals that are diffuse and extended, including high-energy photons associated with dark matter particle decays or annihilation. → extragalactic; → background; → light. |
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