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eye optics caliph physics

Abu al-Hassan ibn al Haytham ( Arabic ) [alha zen ] ( c .965–1038) Egyptian physicist: made major advances in optics.

Alhazen rejected the older idea that light was emitted by the eye, and took the view that light was emitted from self-luminous sources, was reflected and refracted and was perceived by the eye. His book The Treasury of Optics (first published in Latin in 1572) discusses lenses (including that of the eye), plane and curved mirrors, colours and the camera obscura (pinhole camera).

His career in Cairo was nearly disastrous. Born in Basra (now in Iraq), he saw in Cairo the annual flooding of the Nile and persuaded the caliph al-Hakim to sponsor an expedition to southern Egypt with the object of controlling the river and providing an irrigation scheme. Alhazen’s expedition showed him only the difficulties, and on his return he realized that the caliph would probably ensure an unpleasant death for him. To avoid this, he pretended to be mad, and maintained this successfully until the caliph died in 1021. Alhazen then considered studying religion, before turning fully to physics in middle age. His mathematical and experimental approach is the high point of Islamic physics, and his work in optics was not surpassed for 500 years.

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