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Corrective lens. A corrective lens is a transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia. Glasses or "spectacles" are worn on the face a short distance in front of the eye.
Abbe number. In optics and lens design, the Abbe number, also known as the V-number or constringence of a transparent material, is an approximate measure of the material's dispersion (change of refractive index versus wavelength), with high values of V indicating low dispersion. It is named after Ernst Abbe (1840–1905), the German physicist ...
Abe Gubegna was born in Korench Abo, Achefer woreda, near Bahir Dar. His mother was Yigardu Balay, and his father, Gubegna Ambaye, was a farmer. He was one of 11 children in the family. He went to church schools for 12 years, first in his village and then in Gojjam and Begemder. There he learnt Ge'ez and a style of poetry called qene.
Chromatic aberration. Focal length of lens varies with the color of light. In optics, chromatic aberration ( CA ), also called chromatic distortion, color aberration, color fringing, or purple fringing, is a failure of a lens to focus all colors to the same point. [ 1][ 2] It is caused by dispersion: the refractive index of the lens elements ...
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In optics, the Abbe sine condition is a condition that must be fulfilled by a lens or other optical system in order for it to produce sharp images of off-axis as well as on-axis objects. It was formulated by Ernst Abbe in the context of microscopes. [ 1] The Abbe sine condition says that. the sine of the object-space angle should be ...
In order to see a clear image, the eye must focus rays of light on to the light-sensing part of the eye - the retina, which is located in the back of the eye.This focusing - called refraction - is performed mainly by the cornea and the lens, which are located at the front of the eye, the anterior segment.
Website. www .foxitsoftware .com /pdf-reader /. Foxit PDF Reader (formerly Foxit Reader) is a multilingual freemium PDF ( Portable Document Format) tool that can create, view, edit, digitally sign, and print PDF files. [ 3] Foxit Reader is developed by Fuzhou, China-based Foxit Software. Early versions of Foxit Reader were notable for startup ...