Ibn al-Haytham Completes the Book of Optics

Ibn al-Haytham completed his Book of Optics, Kitab al-Manazir, around 1021 while living in Cairo. He argued that vision happens when light enters the eye from objects, rather than when rays leave the eye. He tested his claims with controlled experiments, and he described the camera obscura. The book was translated into Latin and influenced European work on optics.