File:Fresnel lighthouse lens diagram.png

Summary

DescriptionFresnel lighthouse lens diagram.png	English: Section diagram showing how a Fresnel lens (A) in a lighthouse works to collimate light from an oil lamp (L) into a parallel beam. The Fresnel lens, invented in 1822 by Augustin-Jean Fresnel, increased the light projecting power of lighthouses greatly without the weight of a conventional lens of its size. Also shown are mirror strips (m,n) mounted above and below the lens that most lighthouses had, to gather more of the lamp's light. Alterations: removed caption, erased blots in white areas, changed brightness levels to get rid of noise in white areas, sharpened light path lines.
Date	1872
Source	Downloaded from Adolphe Ganot (1872) Natural Philosophy for General Readers and Young Persons, D. Appleton & Co., New York, p.328, fig.257 (translated with permission from Ganot's Cours Élémentaire de Physique by Edmund Atkinson)
Author	Adolphe Ganot
Permission (Reusing this file)	Public domain - Ganot died in 1887; published in USA before 1923

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File:Fresnel lighthouse lens diagram.png

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1872

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