An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 10 Search : refraction
angle of refraction
  زاویه‌ی ِ شکست   
zâviye-yé šekast (#)

Fr.: angle de réfraction   

The angle between the direction in which a ray is refracted and the normal to the refracting surface.

angle; → refraction.

astronomical refraction
  شکست ِ اخترشناختی   
šekast-e axtaršenâxti

Fr.: réfraction astronomique   

The → angular → displacement of a point on the → celestial sphere due to the Earth's → atmospheric refraction.

astronomical; → refraction.

atmospheric refraction
  شکست ِ جوی   
šekast-e javvi

Fr.: réfraction atmosphérique   

The shift in apparent direction of a celestial object caused by the bending of light while passing through the Earth's atmosphere. Since the density of the atmosphere decreases with altitude, the starlight will bend more as it continues down through the atmosphere. As a result, a star will appear higher in the sky than its true direction.

atmospheric; → refraction.

differential refraction
  شکست ِ دگرسانه‌ای   
šekast-e dagarsâneyi

Fr.: refraction différentielle   

A problem encountered in astronomical spectroscopy, which consists of a loss of light from some wavelengths due to → atmospheric dispersion. In simple terms, differential refraction means that at nonzero → zenith distances an object cannot be simultaneously placed at the same position within a → slit at all wavelengths. This problem becomes more important for increasing → airmass, larger → spectral range, and smaller → slitwidths. To remedy this drawback, the slit should always be oriented along a direction perpendicular to the horizon, since differential refraction occurs in that direction.

differential; → refraction.

double refraction
  شکست ِ دوتایی   
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.

geodetic refraction
  شکست ِ زمین‌سنجیک   
šekast-e zamin-sanjik

Fr.: réfraction géodésique   

The limiting case of → astronomical refraction when the light path is entirely within the Earth's atmosphere.

geodetic; → refraction.

horizontal refraction
  شکست ِ افقی   
šekast-e ofoqi (#)

Fr.: réfraction horizontale   

The angular distance of an object below the horizon when it appears to lie on the horizon.

horizontal; → refraction.

index of refraction
  دیشن ِ شکست   
disšan-e šekast

Fr.: indice de réfraction   

Same as → refractive index.

index; → refraction.

law of refraction
  قانون ِ شکست   
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.

refraction
  شکست   
šekast (#)

Fr.: réfraction   

1) Optics: The change of direction which a beam of light undergoes as it enters a medium of different → refractive index.
2) Acoustics: The change in direction in sound waves on reaching the boundary between two media.
3) Seismology: The bending of a seismic wave as it enters a material of different density.

From L.L. refractionem (nominative refractio) "a breaking up," from L. refractus, p.p. of refringere "to break up," from re- "back" + combining form of frangere "to break," from PIE base *bhreg- "to break" (cf. Goth. brikan, O.E. brecan "to break;" Lith. brasketi "crash, crack").

Šekast, past stem of šekastan "to break, split;" Mid.Pers. škastan "to break;" Av. scind-, scand "to beak, cleave;" Proto-Iranian *skand- "to break, cleave;" PIE sken- "to cut off."