Alhazen (the Latinised name of Abu Ali al-Haytham) (965 — 1039) was an Arab scholar and the best-known physicist of the Middle Ages. Born in Basra. He lived and worked in Cairo (Egypt).
His work concerned physics, astronomy, mathematics, medicine and philosophy. Of greatest interest is his research in optics, set out in a treatise which was translated into Latin in the 12th century and circulated in manuscript until the first printed edition (1572). In it Alhazen describes the structure of the eye, following the ancient Greek scholar Galen (131—211 AD), and by means of experiments disproves the ideas of the ancient Greek scholars (Plato, Euclid) of light as rays which issue from the eye and “feel” objects. He put forward his own theory of vision. According to Alhazen, “natural light and coloured rays act upon the eye” and “the visual image is obtained by means of rays which are emitted by visible bodies and enter the eye”. He also held that to every point of the object observed there corresponds a particular receiving point of the eye. He gave a correct account of vision with two eyes. He carried out a number of experiments with the camera obscura, studied the refraction of light, examined the kinds of mirrors (plane, spherical and others), and suggested that light travels at a finite speed.