Verbal form of → diffraction.
A wave property of light which allows it to curl around obstacles whose size is
about that of the wavelength of the light. As a → wavefront
of light passes by an opaque edge or through an opening, secondary weaker wavefronts
are generated, apparently originating at that edge. These secondary wavefronts
with the primary wavefront as well as with each other to form a
→ diffraction pattern.
From Fr. diffraction, from Mod.L. diffractionem, from L. diffrac-, stem of diffringere "break in pieces," from → dis- "apart" + frangere "to break."
Parâš "dispersion, scattering," variant of pâš, pâšidan, → dispersion.
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.
olgu-ye parâš (#)
Fr.: tache de diffraction
A series of concentric rings of dark and light color produced by interference.
Olgu, loanword from Turkish; parâš→ diffraction.
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.
karânmand bé parâš
Fr.: limité par la diffraction
diffuse galactic light
nur-e kahkašâni-ye paxšidé
Fr.: lumière galactique diffuse
Fr.: facteur de dilution
The energy density of a radiation field divided by the equilibrium value for the same color temperature.
Fr.: double réfraction
Formation of two refracted rays of light from a single incident ray; property of certain crystals, notably calcite.
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.
Fr.: facteur d'Eddington
Same as → Eddington parameter.
Fr.: action de Einstein-Hilbert
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.
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 1016 degrees, 102 GeV) prevalent in the early history of the → Universe.
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").
1) Strictly accurate or correct; precise, as opposed to approximate.
Razin "firm, solid, strong" [Dehxodâ, Steingass], Mid.Pers. razên "firm, strong, secure, solid."
Fr.: différentielle exacte
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.
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.
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.