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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. Beyond its primary function of magnification, this simple yet ingenious tool serves a variety of purposes. It can be employed to focus sunlight, harnessing the Sun's rays to create a concentrated hot ...
Grandma's Reading Glass. Grandma's Reading Glass is a 1900 British silent trick film, directed by George Albert Smith, featuring a young boy who borrows a huge magnifying glass to focus on various objects. The film was shot to demonstrate the new technique of close-up. According to Michael Brooke of BFI Screenonline, it "was one of the first ...
By convention, for magnifying glasses and optical microscopes, where the size of the object is a linear dimension and the apparent size is an angle, the magnification is the ratio between the apparent (angular) size as seen in the eyepiece and the angular size of the object when placed at the conventional closest distance of distinct vision: 25 ...
Video magnifier. Video magnifiers are electronic devices that use a camera and a display screen to perform digital magnification of printed materials. The display screen is usually LCD or a similar flat-screen technology (although older video magnifiers have used CRT displays), and the device usually includes a lamp to illuminate the source ...
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.
1 m −1. Illustration of the relationship between optical power in dioptres and focal length in metres. A dioptre ( British spelling) or diopter ( American spelling ), symbol dpt, is a unit of measurement with dimension of reciprocal length, equivalent to one reciprocal metre, 1 dpt = 1 m−1. It is normally used to express the optical power ...
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