Glasses (also called eyeglasses or spectacles) are frames bearing lenses A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens is a lens consisting of a single optical element. A compound lens is an array of simple lenses with a common axis; the use of multiple elements allows more optical aberrations to be corrected worn in front of the eyes Eyes are organs that detect light, and send electrical impulses along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in cnidaria, molluscs, chordates,, normally for vision correction A corrective lens is a lens worn in front of the eye, mainly used to treat myopia, hyperopia, astigmatism, and presbyopia. Glasses or "spectacles" are worn on the face a short distance in front of the eye. Contact lenses are worn directly on the surface of the eye. Intraocular lenses are surgically implanted most commonly after cataract, eye protection Eye protection is protective gear for the eyes, which comes in many types depending upon the threat that is to be reduced. The threats can be particles, light, wind blast, heat, sea spray or some type of ball or puck used in sports, or for protection from UV rays "UV coating" refers to surface treatments which are either cured by ultraviolet radiation, or protect the underlying material from its harmful effects.
Modern glasses are typically supported by pads on the bridge of the nose Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for respiration in conjunction with the mouth. Behind the nose is the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes through the pharynx, shared with the digestive system, and then into the rest of the and by temple arms placed over the ears The ear is the organ that detects sound. The vertebrate ear shows a common biology from fish to humans, with variations in structure according to order and species. It not only acts as a receiver for sound, but plays a major role in the sense of balance and body position. The ear is part of the auditory system. Historical types include the pince-nez Pince-nez are a style of spectacles, popular in the nineteenth century, which are supported without earpieces, by pinching the bridge of the nose. The name comes from the French language - pincer, to pinch, and nez, nose, monocle A monocle is a type of corrective lens used to correct the vision in only one eye. It consists of a circular lens, generally with a wire ring around the circumference that can be attached to a string. The other end of the string is then connected to the wearer's clothing to avoid losing the monocle. The connoisseur of antiquities Philipp von, lorgnette A lorgnette is a pair of spectacles with a handle, used to hold them in place, rather than fitting over the ears. They were invented by an Englishman named George Adams. The lorgnette was usually used as a piece of jewelry, rather than to enhance vision. Fashionable ladies usually preferred them to spectacles. These were very popular at masquerade, and scissors-glasses The invention of scissors-glasses solved the problem of the single lens , by providing two lenses on a "Y" shaped frame. They usually had a ring in the end of the handle so that they could be worn on a ribbon or gold chain around the neck.
Eyeglass lenses are commonly made from plastic Plastic is the general common term for a wide range of synthetic or semisynthetic organic amorphous solid materials used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce costs, including CR-39 CR-39, or allyl diglycol carbonate, is a plastic polymer commonly used in the manufacture of eyeglass lenses. It should not be confused with polycarbonate, a homopolymer made from bis-phenol A, a tough polymer widely used for glazing. CR-39 is a trade marked product of PPG Industries, originally developed by Columbia Chemical Co Inc which evolved and polycarbonate Polycarbonates are a particular group of thermoplastic polymers. They are easily worked, moulded, and thermoformed; as such, these plastics are very widely used in the modern chemical industry. Their interesting features position them between commodity plastics and engineering plastics. Their plastic identification code is 7. These materials reduce the danger of breakage and weigh less than glass lenses. Some plastics also have more advantageous optical properties than glass, such as better transmission of visible light The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 380 to 750 nm. In terms of frequency, this corresponds to a band in the vicinity of 790–400 and greater absorption of ultraviolet light Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet.[1] Some plastics have a greater index of refraction The refractive index of a medium is a measure of how much the speed of light (or other waves such as sound waves) is reduced inside the medium. For example, typical soda-lime glass has a refractive index close to 1.5, which means that in glass, light travels at 1 / 1.5 = 2/3 the speed of light in a vacuum. Two common properties of glass and other than most types of glass; this is useful in the making of corrective lenses shaped to correct various vision abnormalities The World Health Organization publishes a classification of known diseases and injuries called the International Statistical Classification of Diseases and Related Health Problems or ICD-10. This list uses that classification such as myopia Myopia , also called nearsightedness or shortsightedness, is a refractive defect of the eye in which collimated light produces image focus in front of the retina when accommodation is relaxed, allowing thinner lenses for a given prescription An eyeglass prescription is a written order by an optometrist, ophthalmologist, orthoptist or an optician for eyeglasses. It specifies the refractive power to which the eyeglasses are to be made in order to correct blurred vision due to refractive errors, including myopia, hyperopia, astigmatism, and presbyopia. It is typically determined using a. Newer plastic lenses, called izon, can also correct for the higher order aberrations that naturally occur in the surface of our eye.[citation needed] These lenses create sharper vision for the people who have problems with sight and help with the halos, starbursts, and comet-tails often associated with night time driving glare.[citation needed] Wavefront guided LASIK The LASIK technique was made possible by the Colombia-based Spanish ophthalmologist Jose Barraquer, who, around 1950 in his clinic in Bogotá, Colombia, developed the first microkeratome, and developed the technique used to cut thin flaps in the cornea and alter its shape, in a procedure he called keratomileusis. Barraquer also researched the surgery also corrects for the higher order aberrations.
Scratch-resistant coatings can be applied to most plastic lenses giving them similar scratch resistance to glass. Hydrophobic In chemistry, hydrophobicity is the physical property of a molecule (known as a hydrophobe) that is repelled from a mass of water coatings designed to ease cleaning are also available, as are anti-reflective coatings Antireflective or anti-reflection coatings are a type of optical coating applied to the surface of lenses and other optical devices to reduce reflection. This improves the efficiency of the system since less light is lost. In complex systems such as a telescope, the reduction in reflections also improves the contrast of the image by elimination of intended to reduce glare, improve night vision and make the wearer's eyes more visible.[2]
CR-39 lenses are the most common plastic lenses due to their low weight, high scratch resistance, and low transparency for ultra violet and infrared radiation. Polycarbonate and Trivex lenses are the lightest and most shatter-resistant, making them the best for impact protection,[1] though polycarbonate offers poor optics due to high dispersion, having a low Abbe number In physics and optics, the Abbe number, also known as the V-number or constringence of a transparent material, is a measure of the material's dispersion in relation to the refractive index. It is named for Ernst Abbe (1840–1905), the German physicist who defined it of 31.
Not all glasses are designed solely for vision correction but are worn for protection, viewing visual information (such as stereoscopy Stereoscopy, stereoscopic imaging or 3-D imaging is any technique capable of recording three-dimensional visual information or creating the illusion of depth in an image. The illusion of depth in a photograph, movie, or other two-dimensional image is created by presenting a slightly different image to each eye. Many 3D displays use this method to) or simply just for aesthetic or fashion values. Safety glasses are a kind of eye protection Eye protection is protective gear for the eyes, which comes in many types depending upon the threat that is to be reduced. The threats can be particles, light, wind blast, heat, sea spray or some type of ball or puck used in sports against flying debris or against visible and near visible light Light is electromagnetic radiation, particularly radiation of a wavelength that is visible to the human eye . In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not or radiation In physics, radiation describes any process in which energy emitted by one body travels through a medium or through space, ultimately to be absorbed by another body. Non-physicists often associate the word with ionizing radiation , but it can also refer to electromagnetic radiation (i.e., radio waves, infrared light, visible light, ultraviolet. Sunglasses Sunglasses or sun glasses are forms of protective eyewear that usually enclose or protect the eye pupil in order to prevent strong light and uv rays from penetrating. They can sometimes also function as a visual aid, as variously termed spectacles or glasses exist which feature lenses that are colored, polarized or darkened. In the early 20th allow better vision in bright daylight, and may protect against damage from high levels of ultraviolet light Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet.
Contents |
St. Louis Post-Dispatch
Learn about the proper glasses for wine At 6 pm Thursday, the Clayton Straub's store, 8282 Forsyth Boulevard, will host a demonstration of Riedel crystal ...
1027px x 509px | 63.20kB
[source page]
glasses jpg 63 2 KB 172 views
Viveca Pattison
ue, 27 Oct 2009 21:26:45 GM
For nearly the first hour, you probably wouldn't be able to tell Atonement (2007) circumscribes World War II, if watched in mute, that is. The scenes are too lush, blithe and buttered in upper-class ennui to emit the faintest traces...
Q. How many glasses of milk should you drink a day, and is putting ovaltine in it good for you also? Will this help you grow?
Asked by nymetsfan23 - Thu Feb 15 20:03:16 2007 - - 4 Answers - 0 Comments
A. Hi there. I say you should drink 3 glasses a milk a day. One for Breakfast, one for lunch, and one for dinner. Putting ovaltine in milk, I don't think it would hurt anything but it might taste bad. Also of course you will grow, milk keeps you big and strong. Cheers =)
Answered by christian g - Thu Feb 15 20:15:48 2007
