adasi-ye afâm, ~ bifâm
Fr.: lentille achromatique
Lens (or combination of lenses) that brings different wavelengths within a ray of light to a single focus, thus overcoming chromatic aberration.
A lens designed to correct → astigmatism.
Fr.: lentille aplanétique
→ aplanatism; → lens.
Fr.: lentille apochromatique
A lens that is → apochromatic.
adasi-ye Barlow (#)
Fr.: lentille de Barlow
A → negative lens placed in a telescope between the → objective and the → ocular. Its diverging action reduces the convergence of the light cone, forming a larger image at a slightly greater distance.
Peter Barlow (1776-1862), English physicist; → lens.
Fr.: lentille biconcave
Describing a lens with two concave faces.
Fr.: lentille biconvexe
A spherical lens with two convex faces. The radii of curvature for the two surfaces may or may not be the same.
Fr.: effet de lentille du rayonnement du fond cosmique, ~ ~ du CMB
The gravitational effect of the intervening large-scale potentials on the → cosmic microwave background radiation (CMBR). This effect smoothes out the temperature peaks and alters the statistics of the CMB.
Fr.: lentille composée
A lens system consisting of two or more lenses with the same radius used together in order to remove aberrations found in a single lens.
adasi-ye kâv (#)
Fr.: lentille concave
A lens which is thinner at the center than at the edges and diverges the light rays.
adasi-ye kâv-kuž (#)
Fr.: lentille concavo-convexe
A type of → convergent lens that is concave on one surface and convex on the opposite surface. Also called → meniscus lens. Meniscus lenses are used most often in conjunction with another lens to produce an optical system of a longer or shorter → focal length than the original lens.
adasi-ye hammarkaz (#)
Fr.: lentille concentrique
A lens having surfaces whose centers of curvature coincide.
adasi-ye kuž (#)
Fr.: lentille convexe
A lens that converges an incident beam of light to a focus.
→ convex; → lens.
adasi-ye cašm (#)
adasi-ye ostovâneyi (#)
Fr.: lentille cylindrique
A lens in which at least one surface is formed like a portion of a cylinder. Also called astigmatic lens.
The → inflection of nouns, pronouns, or adjectives for case, number, and gender.
M.E. declenson, declynson (with suffix later assimilated to -sion), from O.Fr. declinaison, from L. declinatio, → declination
adasi-ye vâgerâ (#)
Fr.: lentille divergente
A lens which causes a parallel beam of light passing through it to diverge or spread out; concave lens. Same as diverging lens and → negative lens.
Fr.: lentille de champ
A lens placed at or near the focal plane of a telescope to create an image of the primary mirror inside the instrument.
adasi-ye ferenel (#)
Fr.: lentille de Fresnel
An optical lens composed of a series of rings of glass so curved that they all have the same focus. It is flat on one side and ridged on the other making it possible that nearly every ray of light from the source be re-directed out on a horizontal path. This design enables the construction of lenses of large aperture and short focal length avoiding thus the large weights and volumes of material which would be required in conventional lenses. The first Fresnel lens, designed for use in a lighthouse on the river Gironde, was installed in France in 1823, and by the 1850s many examples were in use everywhere. Fresnel lenses are most often used in light gathering applications, such as condenser systems or emitter/detector setups. They can also be used as magnifiers and projection lenses. Nowadays, Fresnel lenses made of optical plastics are widely used for various applications.
adasi-ye gerâneši (#)
Fr.: lentille gravitationnelle
A concentration of matter, such as a galaxy or a cluster of galaxies, that bends light rays from a background object, resulting in production of multiple images. If the two objects and the Earth are perfectly aligned, the light from the distant object appears as a ring from Earth. This is called an Einstein Ring, since its existence was predicted by Einstein in his theory of general relativity.