wave theory of light
negare-ye mowji-ye nur
Fr.: théorie ondulatoire de la lumière
The theory that describes light as waves that spread out from the source that generates the light. It contradicts the → corpuscular theory of light proposed by Newton (1704). The idea of the wave nature of light was first put forward by Robert Hooke (1660). The wave theory was originally stated by Huygens (1690), who showed reflection and refraction could be explained by this theory. It was supported by → Young's experiment (1802) and established by the work of Fresnel (1814-1815). The wave theory received its most important support from Maxwell's → electromagnetic theory. See also → Huygens-Fresnel principle.
qatâr-e mowj (#), mowj-teran
Fr.: train d'onde
A series of successive waves spaced at regular intervals.
bordâr-e mowj (#)
Fr.: vecteur d'onde
A vector whose direction is that of propagation of a wave and whose magnitude is given by the → wave number, 2π/λ, where λ is the → wavelength, or ω/c, where ω is the → angular frequency and c is the speed of propagation.
Fr.: dualité onde-particule
The principle admitted in → quantum mechanics that
all particles have a wave-like nature and that waves have a particle aspect.
The wave-particle duality is of fundamental importance in obtaining a realistic picture of
the → elementary particles.
Fr.: bande de longueur d'onde
A portion of the electromagnetic spectrum which is defined because of its characteristics or for its use.
Fr.: forme d'onde
A graphical representation of the shape of a wave for a given instant in time.
Fr.: analyse de forme d'onde
The resolution of a complex waveform into a sum of simple periodic waves, usually by computer means.
pišân-e mowj, mowj-pišân
Fr.: front d'onde
The locus of adjacent points possessing the same phase in the path of a wave motion. Its surface is uniform (spherical or plane) and normal to propagation direction in an isotropic medium. → wavefront distortion.
aršâyeš-e pišân-e mowj
Fr.: correction de front d'onde
cowlegi-ye pišân-e mowj
Fr.: distortion de front d'onde
The disruption of the spherical shape of a wavefront due to atmospheric turbulence which makes the adjacent points in the wavefront out of phase.
hessgar-e pišân-e mowj
Fr.: analyseur de front d'onde
In adaptive optics, a device that analyzes the light sample coming from the wavefront and determines the error in each part of the beam. The wavefront sensor used in adaptive optics is a → Shack-Hartmann type, which works in conjunction with a deformable mirror.
gerâ-ye pišân-e mowj
Fr.: inclinaison du front d'onde
The average slope in both the X and Y directions of a → wavefront or phase profile across the pupil of an optical system.
Fr.: guide d'ondes
Any transmission medium, such as a hollow metal conductor, coaxial cable, or glass fiber, capable of confining and supporting the propagation of electromagnetic waves regardless of wavelength or mode of propagation.
→ wave; guide, M.E., from O.Fr. guider "to guide, lead," from Frankish *witan "show the way," from P.Gmc. *wit- "to know" (cf. Ger. weisen "to show, point out," wissen "to know;" O.E. witan "to see"). Cognate with Pers. bin- "to see" (present stem of didan "to see"); Mid.Pers. wyn-; O.Pers. vain- "to see;" Av. vaēn- "to see;" Skt. veda "I know;" Gk. oida "I know," idein "to see;" L. videre "to see;" PIE base *weid- "to know, to see."
Mowjbar, from mowj, → wave, + -bar "carrier," from bordan "to carry, lead" (Mid.Pers. burdan, O.Pers./Av. bar- "to bear, carry," barəθre "to bear (infinitive)," Skt. bharati "he carries," Gk. pherein, L. fero "to carry;" PIE base *bher- "to carry").
tul-e mowj (#), mowj-tul (#)
Fr.: longueur d'onde
The distance between two successive points in the wave that are characterized by the same phase of oscillation; e.g. → de Broglie wavelength; → Compton wavelength; → blaze wavelength; → peak wavelength; → center wavelength; → central wavelength; → cutoff wavelength.
A small wave; ripple.
→ wave + -let a diminutive suffix.
Fr.: théorie des ondolettes
A refinement of → Fourier analysis which enables to simplify the description of a complicated function in terms of a small number of coefficients. The formal history of wavelet theory began in the early 1980s when Jean Morlet, a French geophysicist, introduced the concept of wavelet and studied wavelet transform as a new tool for scientific signal analysis. In 1984, his collaboration with Alex Grossmann yielded a detailed mathematical study of the continuous wavelet transforms and their various applications. Although similar results had already been obtained 20-50 years earlier by several other researchers, the rediscovery of the old concepts provided a new method for decomposing functions.
Wilkinson Microwave Anisotropy Probe (WMAP)
A space telescope launched by NASA in 2001 which measures the temperature fluctuations in the → cosmic microwave background (CMB) radiation. It creates a full-sky map of the CMB, with a 13 arcminute resolution via multi-frequency observations. WMAP is the first mission to use a → Lagrangian point L2 as its permanent observing station at a distance of 1.5 million km. WMAP completed its prime two years of mission operations in September 2003 and is continuing in 2009 its observations for still several years to come. WMAP's measurements have played a considerable role in establishing the current standard model of cosmology. They are consistent with a Universe that is dominated by → dark energy, with negative pressure or a → cosmological constant. In this model, the age of the Universe is 13.73 ± 0.12 billion years. The current expansion rate of the Universe measured by the Hubble constant, is 70.5 ± 1.3 km·s-1 Mpc-1. The content of the Universe consists of 4.56% ± 0.15% ordinary → baryonic matter, 22.8% ± 1.3% → cold dark matter, and 72.6% ± 1.5% of → dark energy, that accelerates the → expansion of the Universe.
WMAP, short for Wilkinson Microwave Anisotropy Probe, in honor of David Todd Wilkinson (1935-2002), who had been a member of the mission's science team.