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The purpose of a magnifying glass is to enlarge items or elements that could otherwise not be seen with the naked eye. In the past, magnifying glasses have been useful in science and forensics.
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The earliest known version of a magnifying glass, or rather, a convex lens, came about in the year 1021 and was mentioned in Alhazen's Book of Optics. Improvements upon the lens ultimately led to the invention of eyeglasses in the 13th century.
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The presence of the magnifying glass in the modern world has opened our eyes to things we never would have been capable of seeing before. Without the amplifying abilities of a convex lens, the telescope would not have come across new stars and planets and the microscope would not have stumbled upon undiscovered cells and organisms.
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The efficacy of a magnifying glass is dependent upon its placement in relation to one's eye. The closer the object is to the eye without becoming hazy or clouded, the more visibility one will have. Because of this phenomenon, called the near point, there are numerous amplification sizes for a magnifying glass.
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The two most technical features of a magnifying glass are its focal length and its optical power. A standard magnifying glass has a focal length of about 25 centimeters, which means its optical power would be 4 dioptres (in laymen's terms, this would be a 2x magnification level).
