A magnifying glass (called a hand lens in laboratory contexts) is a convex lens which is used to produce a magnified image of an object. A lens is an optical device with perfect or approximate Axial symmetry which transmits and refracts Light, converging or diverging Magnification is the process of enlarging something only in appearance not in physical size An image (from Latin imago) or picture is an artifact usually two-dimensional that has a similar appearance to some subject &mdashusually The lens is usually mounted in a frame with a handle (see image). A lens is an optical device with perfect or approximate Axial symmetry which transmits and refracts Light, converging or diverging Roger Bacon is the original inventor of the magnifying glass. For the Nova Scotia premier see Roger Bacon (politician. Roger Bacon, O
A magnifying glass works by creating a magnified virtual image of an object behind the lens. In Optics, a virtual image is an image in which the outgoing rays from a point on the object never actually intersect at a point The distance between the lens and the object must be shorter than the focal length of the lens for this to occur. The focal length of an optical system is a measure of how strongly it converges (focuses or diverges (diffuses Light. Otherwise, the image appears smaller and inverted, and can be used to project images onto surfaces.
The framed lens may be mounted on a stand, keeping the lens at the right distance from the table, and therefore at the right distance from the object on the table. The latter applies if the object is small, and also if the height is adjustable. Some magnifying glasses are foldable (from the handle or stand).
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. A Fresnel lens (pronounced or) is a type of lens invented by French physicist Augustin-Jean Fresnel.
A loupe is a small magnification device used by surgeons, dentists, jewelers, watchmakers, and other precision craftsmen. A loupe (pronounced loop) is a type of Magnification device used to see things one is looking at more closely In Medicine, a surgeon is a person who performs Surgery. Surgery is a broad category of invasive Medical treatment that involves the cutting of a Jewellery (also spelled jewelry, see spelling differences) is a personal Ornament, such as a necklace ring or bracelet made from Gemstones A watchmaker is an Artisan who makes and repairs Watches A modern watchmaker is more likely to repair a wristwatch or a pocketwatch than to actually create a watch The magnification of jewelers' loupes for studying gemstones is typically on the order of 10×. [1]
The magnifying glass is an icon of detective fiction, particularly that of Sherlock Holmes. Detective fiction is a branch of Crime fiction in which a Detective (or detectives either professional or amateur investigate a crime usually Murder Sherlock Holmes is a famous fictional detective of the late nineteenth and early twentieth centuries who first appeared in Publication in 1887
Visually impaired people often benefit from magnifying glasses and similar low vision aids. Visual impairment or vision impairment is Vision loss that constitutes a significant limitation of visual capability resulting from Disease, Low vision is a subspecialty within the professions of Optometry and Ophthalmology and Opticianry dealing with individuals who have less than normal vision
Magnification
The magnification of a magnifying glass depends on where it is placed between the user's eye and the object being viewed, and the total distance between the eye and the object. Magnification is the process of enlarging something only in appearance not in physical size Magnifying glasses are typically described in terms of their magnifying power, which is equivalent to angular magnification (this should not be confused with optical power, which is a different quantity). Magnification is the process of enlarging something only in appearance not in physical size Optical power ( dioptric power or refractive power) is the degree to which a lens or Mirror converges or diverges light The magnifying power is the ratio of the sizes of the images formed on the user's retina with and without the lens. [2] For the "without" case, it is typically assumed that the user would bring the object as close to the eye as possible without it becoming blurry. This point, known as the near point, varies with age. Presbyopia (Greek word "presbys" (πρέσβυς meaning "old person" describes the condition where the Eye exhibits a progressively diminished ability In a young child it can be as close as 5 cm, while in an elderly person it may be as far as one or two metres. Magnifiers are typically characterized using a "standard" value of 0. 25 m.
The highest magnifying power is obtained by putting the lens very close to the eye and moving the eye and the lens together to obtain the best focus. The object will then typically also be close to the lens. The magnifying power obtained in this condition is MP0=¼Φ+1, where Φ is the optical power in dioptres, and the factor of ¼ comes from the assumed distance to the near point. A dioptre, or diopter, is a Unit of measurement of the Optical power of a lens or curved Mirror, which is equal to the reciprocal This value of the magnifying power is the one normally used to characterize magnifiers. It is typically denoted "m×", where m=MP0. This is sometimes called the total power of the magnifier (again, not to be confused with optical power).
Magnifiers are not always used as described above, however. It is much more comfortable to put the magnifier close to the object (one focal length away). The eye can then be a larger distance away, and a good image can be obtained very easily; the focus is not very sensitive to the eye's exact position. The magnifying power in this case is roughly MP=¼Φ.
A typical magnifying glass might have a focal length of 25 cm, corresponding to an optical power of 4 dioptres. The focal length of an optical system is a measure of how strongly it converges (focuses or diverges (diffuses Light. Such a magnifier would be sold as a "2×" magnifier. In actual use, an observer with "typical" eyes would obtain a magnifying power between 1 and 2, depending on where lens is held. An older person might obtain an actual magnifying power of 8 or more with this lens, however, due to the eye's longer near point distance.
See also
References
- ^ Wickell, Carly. A burning-glass is a large convex lens that can concentrate the Sun 's rays onto a small area heating up the area and thus resulting in ignition of the Glasses, also called eyeglasses or spectacles, are frames bearing lenses worn in front of the Eyes normally for vision correction, See also Magnifying glass A screen magnifier is software that interfaces with a computer's graphical output to present enlarged screen content A loupe (pronounced loop) is a type of Magnification device used to see things one is looking at more closely Jeweler's Loupe. About: Jewelry / Accessories. About. com. Retrieved on 2007-02-20. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1472 - Orkney and Shetland are left by Norway to Scotland, due to a Dowry payment
- ^ Hecht, Eugene (1987). Optics, 2nd ed. , Addison Wesley, pp. 186-188. ISBN 0-201-11609-X.
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