Ibn al-Haytham (c. 965–1040), known in the Latin world as "Alhazen," was a great physicist, mathematician, and astronomer born in Basra. He spent a significant part of his life in Cairo.
In his seven-volume masterpiece "Kitab al-Manazir" (Book of Optics), he proved experimentally that vision occurs not by light leaving the eye and traveling to the object, but by light reflected from the object reaching the eye. He explained the principle of the camera obscura (dark chamber), and with his method grounded in experiment and mathematical proof he is regarded as the founder of the modern scientific method and of optics. His works were translated into Latin and influenced scholars such as Roger Bacon and Kepler.