A Magnifying Glass also known as Hand Lens, is a convex lens which is used to produce a magnified image of an object. The lens is usually mounted in a frame with a handle. A Magnifying Glass works by creating a magnified virtual image of an object behind the lens. The distance between the lens and the object must be shorter than the focal length of the lens for this to occur. 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 fordable (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 Loupe is a small magnification device used by surgeons, dentists, jewellers, watchmakers, and other precision craftsmen. The magnification of jewellers' loupes for studying gemstones is typically on the order of 10×.
History of Invention
Magnifying Glass is one of the most ancient optical (related to the eye) devices known to science. Thousands of years ago Egyptians used chips of crystal or obsidian (a type of shiny stone) to better view small objects. In Rome Emperor Nero ( A.D. 37-68) was known to have peered through gemstones at actors on a distant stage. The first magnifier constructed for scientific purposes is believed to have been designed by the English philosopher Roger Bacon in 1250. He was an Englishman and a lecturer at the University of Oxford. He made various experiments with Magnifying Glasses and mirrors and described the principles of reflection and refraction. The study of optics in part five of Opus Majus seems to draw on the works of the Muslim scientists, Alkindus (al-Kindi) and Alhazen (Ibn al-Haytham), including a discussion of the physiology of eyesight, the anatomy of the eye and the brain, and considers light, distance, position, and size, direct vision, reflected vision, and refraction, mirrors and lenses. His research in optics was primarily oriented by the legacy of Alhazen (Ibn al-Haytham; d. 1041) through a Latin translation of the latter's monumental Kitab al-manazir (De aspectibus; Perspectivae; The Optics), while the impact of the tradition of al-Kindi (Alkindus) was principally mediated through the influence that this Arabic scholar had on the optics of Robert Grosseteste. Moreover, Bacon's investigations of the properties of the Magnifying Glass partly rested on the handed down legacy of Arab opticians; mainly Ibn al-Haytham (Alhazen), who was in his turn influenced by Ibn Sahl's 10th century legacy in dioptrics.
Role of Magnifying Glass in the Improvement Of Human Life
Visually impaired people often benefited from Magnifying Glasses and similar low vision aids.
The use of a magnifying lens to improve reading led to hypothesize that strong lenses which later became telescopes, might enable humans to see objects extremely farther away.
It also led to later inventions such as microscopes and spectacles