Kirchhoff's law qânun-e Kirchhoff (#) Fr.: loi de Kirchhoff The radiation law which states that at thermal equilibrium the ratio of the energy emitted by a body to the energy absorbed by it depends only on the temperature of the body. Gustav Robert Kirchhoff (1824-1887), a German physicist who made major contributions to the understanding of electric circuits, spectroscopy, and the emission of black-body radiation from heated objects; → law. |
Kleinmann-Law nebula miq-e Kainman-Law Fr.: nébuleuse de Kleinmann-Law An strong, extended infrared source in the Orion Nebula, about 1 arcminute NW of the Trapezium and about 12 arcseconds south of the → Becklin-Neugebauer object. It dominates the infrared emission at wavelengths above 20 microns. It probably represents a cluster of young and forming stars embedded in a dusty molecular cloud. Named after Douglas E. Kleinmann (1942-) and Frank J. Low (1933-), who first studied this object in 1967; → nebula. |
Kramers' law qânun-e Kramers (#) Fr.: loi de Kramers An approximate expression for deriving the → opacity that depends upon temperature with a power law: κ ∝ ρT^{-3.5}, where ρ represents the density. In → partial ionization zones, a part of the energy released during a layer's compression can be used for further ionization, rather than raising the temperature of the gas. As the temperature of the compressed layer has not substantially increased, the increase in density produces a corresponding increase in the opacity of the layer. Likewise, during the expansion phase, the temperature does not decrease significantly since the ions release energy when they recombine with electrons. Derived in 1923 by the Dutch physicist Henrik Kramers (1894-1952); → law. |
Kramers' opacity law qânun-e kederi-ye Kramers (#) Fr.: loi de l'opacité de Kramers Same as → Kramers' law. Named after Henrik Kramers (1894-1952); → law. |
Lambert's cosine law qânun-e cosinus-e Lambert Fr.: loi en cosinus de Lambert The intensity of the light emanating in any given direction from a perfectly diffusing surface is proportional to the cosine of the angle between the direction and the normal to the surface. Also called → Lambert's law. |
Lambert's law qânun-e Lambert Fr.: loi de Lambert Same as → Lambert's cosine law. |
law qânun (#), arté (#) Fr.: loi 1) A rule of conduct or procedure established by custom, agreement,
or authority. M.E., O.E. lagu, from O.N. *lagu, variant of lag "that which is laid down;" cf. Ger. liegen, E. lay, lie; PIE *legh- "To lie, lay;" compare with Hittite laggari "falls, lies," Gk. lekhesthai "to lie down," L. lectus "bed," O.Ir. lige "bed, tomb," Tokharian lake, leke "bed." Qânun, from Ar., ultimately from Gk. kanon "rule." |
law of cosines qânun-e kosinushâ Fr.: loi des cosinus An expression that for any triangle relates the length of a side to the cosine of the opposite angle and the lengths of the two other sides. If a, b, and c are the sides and A, B, and C are the corresponding opposites angles: a^{2} = b^{2} + c^{2} - 2bc cos A; b^{2} = c^{2} + a^{2} - 2ca cos B; c^{2} = a^{2} + b^{2} - 2ab cos C. |
law of excluded middle qânun-e miyâni soklândé Fr.: principe du milieu exclu Same as → principle of excluded middle. |
law of identity qânun-e idâni Fr.: principe d'identité Same as → principle of identity. |
law of inertia qânun-e laxti (#) Fr.: loi d'inertie Same as → Newton's first law. The → reference frames to which the law applies are called → inertial frames. |
law of non-contradiction qânun-e nâpâdguyi Fr.: principe de non-contradiction Same as → principle of non-contradiction. → law; → non-; → contradiction. |
law of reflection qânun-e bâztâb (#) Fr.: loi de réflexion One of the two laws governing reflection of light from a surface: a) The → incident ray, normal to surface, and reflected ray lie in the same plane. b) The → angle of incidence (with the normal to the surface) is equal to the → angle of reflection. → law; → reflection. |
law of refraction qânun-e šekast (#) Fr.: loi de réfraction One of the two laws governing → refraction of light when it enters another transparent medium: a) The → incident ray, normal to the surface, and refracted ray, all lie in the same plane. b) → Snell's law is satisfied. → law; → refraction. |
law of sines qânun-e sinushâ Fr.: loi des sinus In any triangle the sides are proportional to the sines of the opposite angles: a/sin A = b/sin B = c/sin C, where A, B, and C are the three vertices and a, b, and c are the corresponding sides. |
lawrencium lawrensiom (#) Fr.: lawrencium An artificially produced → radioactive→ chemical element; symbol Lr (formerly Lw). → Atomic number 103; → atomic weight of most stable isotope 262; → melting point about 1,627°C; → boiling point and → specific gravity unknown; → valence +3. The longest half-life associated with this unstable element is 3.6 hour ^{262}Lr. Credit for the first synthesis of this element in 1971 is given jointly to American chemists from the University of California laboratory in Berkeley under Albert Ghiorso and the Russian team at the Joint Institute for Nuclear Reactions lab in Dubna, under Georgi N. Flerov. Named the American physicist Ernest 0. Lawrence (1901-1958), who developed the → cyclotron, + → -ium. |
laws of dynamics qânunhâ-ye tavânik Fr.: lois de dynamique The three basic laws of → dynamics which were first formulated by Isaac Newton in his classical work "Mathematical Principles of Natural Philosophy" published in 1687. → Newton's first law of motion; → Newton's second law of motion; → Newton's third law of motion. |
Leavitt law qânun-e Leavitt Fr.: loi de Leavitt Same as the → period-luminosity relation. Named after Henrietta Swan Leavitt (1868-1921), American woman astronomer, who discovered the relation between the luminosity and the period of → Cepheid variables (1912); → law. |
Lenz's law qânun-e Lenz (#) Fr.: loi de Lenz The direction of an induced current is such as to oppose the cause producing it. The cause of the current may be the motion of a conductor in a magnetic field, or it may be the change of flux through a stationary circuit. Named after Heinrich Friedrich Emil Lenz (1804-1865), German physicist, who published the law in 1834; → law. |
Malus' law qânun-e Malus (#) Fr.: loi de Malus If the light wave entering an → analyzer is → linearly polarized, the intensity of the wave emerging from the analyzer is I = k I_{0} cos^{2}φ, where k is the coefficient of transmission of the analyzer, I_{0} is the intensity of the incident light, and φ is the angle between the planes of → polarization of the incident light and the light emerging from the analyzer. Named after Etienne Louis Malus (1775-1812), French physicist who also discovered polarization by reflection at a glass surface (1808); → law. |