Lens (optics)

A lens is a device for either concentrating or diverging light, usually formed from a piece of shaped glass. Analogous devices used with other types of electromagnetic radiation are also called lenses: for instance, a microwave lens can be made from paraffin wax.

Related Topics:
Light - Glass - Electromagnetic radiation - Microwave - Paraffin wax

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The earliest records of lenses date to Ancient Greece, with Aristophanes' play The Clouds (424 BC) mentioning a burning-glass (a convex lens used to focus the sun's rays to produce fire). The writings of Pliny the Elder (23-79) also show that burning-glasses were known to the Roman Empire, and mentions what is possibly the first use of a corrective lens: Nero was known to watch the gladiatorial games through a concave-shaped emerald (presumably to correct for myopia). Seneca the Younger (3 BC--65) described the magnifying effect of a glass globe filled with water. The Arabian mathematician Alhazen (Abu Ali al-Hasan Ibn Al-Haitham), (965-1038) wrote the first major optical treatise which described how the lens in the human eye formed an image on the retina. Widespread use of lenses did not occur until the invention of spectacles, probably in Italy in the 1280s.

Related Topics:
Ancient Greece - Aristophanes - The Clouds - 424 BC - Burning-glass - Sun - Pliny the Elder - 23 - 79 - Roman Empire - Corrective lens - Nero - Gladiatorial games - Emerald - Myopia - Seneca the Younger - 3 BC - 65 - Water - Alhazen (Abu Ali al-Hasan Ibn Al-Haitham) - 965 - 1038 - Lens - Eye - Retina - Spectacles - Italy - 1280s

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