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Coddington Magnifier
A Coddington magnifier is a magnifying glass consisting of a single very thick lens with a central deep groove diaphragm at the '' equator'', thus limiting the rays to those close to the axis, which minimizes spherical aberration. This allows for greater magnification than a conventional magnifying glass, typically 10× up to 20×. Most single lens magnifiers are limited to 5× or so before significant distortion occurs. The drawback is that the diaphragm groove reduces the area seen through the magnifier. History In 1812 William Hyde Wollaston introduced a much improved version of the earliest magnifiers consisting of a spherical glass by employing two hemispheres of glass mounted together with a small stop between them. Sir David Brewster found that Wollaston's form worked best when the two lenses were hemispheres and the central space was filled up with a transparent cement having the same refractive index as the glass. He therefore used a sphere from a single piece of glas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnifying Glass
A magnifying glass is a convex lens that is used to produce a magnified image of an object. The lens is usually mounted in a frame with a handle. A magnifying glass can be used to focus light, such as to concentrate the sun's radiation to create a hot spot at the focus for fire starting. A sheet magnifier consists of many very narrow concentric ring-shaped lenses, such that the combination acts as a single lens but is much thinner. This arrangement is known as a Fresnel lens. The magnifying glass is an icon of detective fiction, particularly that of Sherlock Holmes. History "The evidence indicates that the use of lenses was widespread throughout the Middle East and the Mediterranean basin over several millennia". The earliest explicit written evidence of a magnifying device is a joke in Aristophanes's '' The Clouds'' from 424 BC, where magnifying lenses to ignite tinder were sold in a pharmacy, and Pliny the Elder's "lens", a glass globe filled with water, used to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lens (optics)
A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), usually arranged along a common axis. Lenses are made from materials such as glass or plastic, and are ground and polished or molded to a desired shape. A lens can focus light to form an image, unlike a prism, which refracts light without focusing. Devices that similarly focus or disperse waves and radiation other than visible light are also called lenses, such as microwave lenses, electron lenses, acoustic lenses, or explosive lenses. Lenses are used in various imaging devices like telescopes, binoculars and cameras. They are also used as visual aids in glasses to correct defects of vision such as myopia and hypermetropia. History The word ''lens'' comes from '' lēns'', the Latin name of the lentil (a seed of a lent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equator (other)
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and midway between the poles. On Earth, ''the Equator'', at 0° latitude, divides the Northern and Southern Hemispheres. Equator may also refer to: Geography and astronomy * Celestial equator * Thermal equator * Solar equator * Chemical equator * Equatorial bulge Film and television * Equator HD, a geography-themed television network that broadcasts in high-definition * Equator (BBC TV series), ''Equator'' (BBC TV series), a 2006 documentary series based on a journey along the equator * Man from the Equator, ''The Equator Man'', a 2012 South Korean television series Literature and periodicals * The Equator (newspaper), ''The Equator'' (newspaper), a 19th-century black issues newspaper * ''Following the Equator'', an 1897 social commentary and travelogue by Mark Twain Music * Equator Records, a Kenya-based record label active from 1960 to 1974 * Equator Records (Ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spherical Aberration
In optics, spherical aberration (SA) is a type of aberration found in optical systems that have elements with spherical surfaces. Lenses and curved mirrors are prime examples, because this shape is easier to manufacture. Light rays that strike a spherical surface off-centre are refracted or reflected more or less than those that strike close to the centre. This deviation reduces the quality of images produced by optical systems. Overview A spherical lens has an aplanatic point (i.e., no spherical aberration) only at a radius that equals the radius of the sphere divided by the index of refraction of the lens material. A typical value of refractive index for crown glass is 1.5 (see list), which indicates that only about 43% of the area (67% of diameter) of a spherical lens is useful. It is often considered to be an imperfection of telescopes and other instruments which makes their focusing less than ideal due to the spherical shape of lenses and mirrors. This is an imp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnification
Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a calculated number also called "magnification". When this number is less than one, it refers to a reduction in size, sometimes called ''minification'' or ''de-magnification''. Typically, magnification is related to scaling up visuals or images to be able to see more detail, increasing resolution, using microscope, printing techniques, or digital processing. In all cases, the magnification of the image does not change the perspective of the image. Examples of magnification Some optical instruments provide visual aid by magnifying small or distant subjects. * A magnifying glass, which uses a positive (convex) lens to make things look bigger by allowing the user to hold them closer to their eye. * A telescope, which uses its large objective lens or primary mirror to create an image of a distant object and then allows the user to examine the imag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Hyde Wollaston
William Hyde Wollaston (; 6 August 1766 – 22 December 1828) was an English chemist and physicist who is famous for discovering the chemical elements palladium and rhodium. He also developed a way to process platinum ore into malleable ingots.Melvyn C. UsselmanWilliam Hyde WollastonEncyclopædia Britannica, retrieved 31 March 2013 Life He was born in East Dereham in Norfolk, the son of the Francis Wollaston (1737–1815), a noted amateur astronomer, and his wife Althea Hyde. He was one of 17 children, but the family was financially well-off and he enjoyed an intellectually stimulating environment. He was educated privately (and remotely) at Charterhouse School from 1774 to 1778 then studied Sciences at Gonville and Caius College, Cambridge. In 1793 he obtained his doctorate (MD) in medicine from Cambridge University, and was a Fellow of his college from 1787 to 1828. He worked as a physician in Huntingdon from 1789 then moved to Bury St Edmunds before moving to London in 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sir David Brewster
Sir David Brewster KH PRSE FRS FSA Scot FSSA MICE (11 December 178110 February 1868) was a British scientist, inventor, author, and academic administrator. In science he is principally remembered for his experimental work in physical optics, mostly concerned with the study of the polarization of light and including the discovery of Brewster's angle. He studied the birefringence of crystals under compression and discovered photoelasticity, thereby creating the field of optical mineralogy.A. D. Morrison-Low (2004) "Brewster, Sir David (1781–1868)" in ''Oxford Dictionary of National Biography'' For this work, William Whewell dubbed him the "father of modern experimental optics" and "the Johannes Kepler of optics." A pioneer in photography, Brewster invented an improved stereoscope, which he called "lenticular stereoscope" and which became the first portable 3D-viewing device. He also invented the stereoscopic camera, two types of polarimeters, the polyzonal lens, the lighth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refractive Index
In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or refracted, when entering a material. This is described by Snell's law of refraction, , where ''θ''1 and ''θ''2 are the angle of incidence and angle of refraction, respectively, of a ray crossing the interface between two media with refractive indices ''n''1 and ''n''2. The refractive indices also determine the amount of light that is reflected when reaching the interface, as well as the critical angle for total internal reflection, their intensity ( Fresnel's equations) and Brewster's angle. The refractive index can be seen as the factor by which the speed and the wavelength of the radiation are reduced with respect to their vacuum values: the speed of light in a medium is , and similarly the wavelength in that medium is , where ''� ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henry Coddington
Henry Coddington (1798/9, Oldbridge, County Meath — 3 March 1845, Rome) was an Anglo Irish natural philosopher, fellow and tutor of Trinity College, Cambridge and Church of England clergyman. Life Henry Coddington was the son of Latham Coddington, Rector of Timolin, Kildare. Admitted to Trinity College, Cambridge in 1816, Coddingtion graduated BA as Senior Wrangler in 1820, and first Smith's prizeman; proceeded M.A. in 1823, and obtained a fellowship and sub-tutorship in his college. He retired to the college living of Ware in Hertfordshire, and in the discharge of his clerical duties burst a blood-vessel, thereby fatally injuring his health. Coddington was vicar of Ware, Hertfordshire from 1832 to 1845. Advised to try a southern climate, he travelled abroad, and died at Rome 3 March 1845. Family He married a daughter of Dr. Batten, principal of Haileybury College, and left seven children. Legacy He wrote chiefly on optics, in particular ''An Elementary Treatise on Optics ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stanhope Lens
A Stanhope lens is a simple, one-piece microscope invented by Charles, the third Earl of Stanhope. It is a cylinder of glass with each end curved outwards, one being more convex than the other. The focal length of the apparatus is at or within the device so that objects to be studied are placed close to or in contact with the less curved end. Because its construction is simple and economical, it was popular in the 19th century. It was useful in medical practice for examining transparent materials such as crystals and fluids. René Dagron modified the lens by keeping one curved end to refract light while sectioning the other end flat and locating it at the focal plane of the curved side.The Strad Dagron used the modified Stanhope lens in mounting his microscopic pictures in photographic jewels known as [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
