Muslim personage

Abu Ali Al-Hasan Ibn Al-Hasan (or al-Husain) Ibn Al-Haitham. Born c. 965 in Basra (Iraq), he flourished in Egypt under Al-Hakim (996 to 1020) and died in Cairo in 1039 or soon after.

He was arguably the greatest Muslim physicist and one of the greatest students of optics of all time. He was also an astronomer, a mathematician, a physician, and he wrote commentaries on Aristotle and Galen. He wrote about 70 manuscripts and he had propounded the famous Snell's law about 600 years before Snell.

The Latin translation of his main work, the Optics (kitab al-manazir), exerted a great influence upon Western science (R. Bacon; Kepler). It showed a great progress in the experimental method. Research in catoptrics: spherical and parabolic mirrors, spherical aberration; in dioptrics: the ratio between the angle and incidence and refraction does not remain constant; magnifying power of a lens. study of atmospheric refraction. The twilight on ly ceases or begins when the sun is 19o below the horizon; attempt to measure the height of the atmosphere on that basis. Better description of the eye, and better understanding of vision, though ibn al-haitham considered the lens as the sensitive part; the rays originate in the object seen, not in the eye. Attempt to explain binocular vision. Correct explanation of the apparent increase in the size the sun and the moon when near the horizon. earliest use of the camera obscura.

The catoptrics contain the following problem, known as Alhazen's problem: from two points of the plane of a circle to draw lines meeting at point of the circumference and making equal angles with the normal at that point. It leads to an equation of the fourth degree. Alhazen solved it by the aid of an hyberpola intersecting a circle. He also solved the so-called al-Mahani's (cubic) equation (q. v., second half of the ninth century) in a similar (Archimedian) manner.

by: Natasha Sopieva