YAMOUT OPTICAL CENTER

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Al-Haitham 965 - 1040 C.E.

Al-Haitham, known in the West as Alhazen, is considered as the father of modern Optics. Abu Ali Hasan Ibn al-Haitham was one of the most eminent physicists, whose contributions to optics and the scientific methods are outstanding. Ibn al-Haitham was born in 965 C.E. in Basra (present Iraq), and received his education in Basra and Baghdad. He traveled to Egypt and Spain. He spent most of his life in Spain, where conducted research in optics, mathematics, physics, medicine and development of scientific methods.

Al-Haitham conducted experiments on the propagation of light and colors, optic illusions and reflections. He examined the refraction of light rays through transparent medium (air, water) and discovered the laws of refraction. He also carried out the first experiments on the dispersion of light into its constituent colors. In detailing his experiment with spherical segments (glass vessels filled with water), he came very close to discovering the theory of magnifying lenses, which was developed in Italy three centuries later. It took another three centuries before the law of sins was proposed by Snell and Descartes.

His book Kitab-al-Manazir was translated into Latin in the Middle Ages, as also his book dealing with the colors of sunset. He dealt at length with the theory of various physical phenomena such as the rainbow, shadows, eclipses, and speculated on the physical nature of light. Roger Bacon (thirteenth century), Pole Witelo (Vitellio) and all Medieval Western writers on Optics base their optical work primarily on Al-Haitham's 'Optical Thesaurus.' His work also influenced Leonardo da Vinci and Johan Kepler. His approach to optics generated fresh ideas and resulted in great progress in experimental methods.

Al-Haitham was the first to describe accurately the various parts of the eye and gave a scientific explanation of the process of vision. He contradicted Ptolemy's and Euclid's theory of vision that the eye sends out visual rays to the object of the vision; according to him the rays originate in the object of vision and not in the eye. He also attempted to explain binocular vision, and gave a correct explanation of the apparent increase in size of the sun and the moon when near the horizon. He is known for the earliest use of the Camera obscura. Through these extensive researches on optics, he has been considered as the father of modern Optics.

In Al-Haitham's writings, one finds a clear explanation of the development of scientific methods as developed and applied by the Muslims, the systematic observation of physical phenomena and their relationship to a scientific theory. This was a major breakthrough in scientific methodology, as distinct from guesswork, and placed scientific study on a sound foundation comprising systematic relationship between observation, hypothesis and verification.

His research in catoptrics focused on spherical and parabolic mirrors and spherical aberration. He made the important observation that the ratio between the angle of incidence and refraction does not remain constant and investigated the magnifying power of a lens. His catoptrics contains the important problem known as Alhazen's problem. It comprises drawing lines from two points in the plane of a circle meeting at a point on the circumference and making equal angles with the normal at that point. This leads to an equation of the fourth degree. He also solved the shape of an aplantic surface for reflection.

In his book Mizan al-Hikmah, Al-Haitham has discussed the density of the atmosphere and developed a relation between it and the height. He also studied atmospheric refraction. He discovered that the twilight only ceases or begins when the sun is 19^o below the horizon and attempted to measure the height of the atmosphere on that basis. He deduced the height of homogeneous atmosphere to be fifty-five miles.

Al-Haitham's contribution to mathematics and physics is extensive. In mathematics, he developed analytical geometry by establishing linkage between algebra and geometry. In Physics, he studied the mechanics of motion of a body and was the first to propose that a body moves perpetually unless an external force stops it or changes its direction of motion. This is strikingly similar to the first law of motion. He has also discussed the theories of attraction between masses, and it appears that he was aware of the magnitude of acceleration due to gravity.

Al-Haitham wrote more than two hundred books, very few of which have survived. His monumental treatise on optics has survived through its Latin translation. During the Middle Ages his books on cosmology were translated into Latin, Hebrew and other European languages. Also, he wrote a book on the subject of evolution; the ideas contained in that book are worth reading and useful even today.

Al-Haitham's influence on physical sciences in general, and optics in particular, has been held in high esteem and his ideas heralded in a new era in both the theoretical and experimental optical research. He wrote commentaries on Aristotle, Galen, Euclid and Ptolemy. Beer and Medler in their famous work Der Mond (1837) mention one of the surface features of the moon after Alhazen.

Abu Ali Hasan Ibn al-Haitham was one of the most eminent physicists, whose contributions to optics and the scientific methods are outstanding. Known in the West as Alhazen, Ibn al-Haitham was born in 965 A.D. in Basra, and was educated in Basra and Baghdad. Thereafter, he went to Egypt, where he was asked to find ways of controlling the flood of the Nile. Being unsuccessful in this, he feigned madness until the death of Caliph al-Hakim. He also traveled to Spain and, during this period, he had ample time for his scientific pursuits, which included optics, mathematics, physics, medicine and development of scientific methods on each of which he has left several outstanding books.

He made a thorough examination of the passage of light through various media and discovered the laws of refraction. He also carried out the first experiments on the dispersion of light into its constituent colors. His book Kitabal Manadhir was translated into Latin in the Middle Ages, as also his book dealing with the colors of sunset. He dealt at length with the theory of various physical phenomena like shadows, eclipses, the rainbow, and speculated on the physical nature of light. He is the first to describe accurately the various parts of the eye and give a scientific explanation of the process of vision. He also attempted to explain binocular vision, and gave a correct explanation of the apparent increase in size of the sun and the moon when near the horizon. He is known for the earliest use of the camera obscura. He contradicted Ptolemy's and Euclid's theory of vision that objects are seen by rays of light emanating from the eyes; according to him the rays originate in the object of vision and not in the eye. Through these extensive researches on optics, he has been considered as the father of modern Optics.

      The Latin translation of his main work, Kitabal Manadhir, exerted a great influence upon Western science e.g. on the work of Roger Bacon and Kepler. It brought about a great progress in experimental methods. His research in catoptrics centered on spherical and parabolic mirrors and spherical aberration. He made the important observation that the ratio between the angle of incidence and refraction does not remain constant and investigated the magnifying power of a lens. His catoptrics contains the important problem known as Alhazen's problem. It comprises drawing lines from two points in the plane of a circle meeting at a point on the circumference and making equal angles with the normal at that point. This leads to an equation of the fourth degree.

      In his book Mizan al-Hikmah Ibn al-Haitham has discussed the density of the atmosphere and developed a relation between it and the height. He also studied atmospheric refraction. He discovered that the twilight only ceases or begins when the sun is 19 deg. below the horizon and attempted to measure the height of the atmosphere on that basis. He has also discussed the theories of attraction between masses, and it seems that he was aware of the magnitude of acceleration due to gravity.

      His contribution to mathematics and physics was extensive. In mathematics, he developed analytical geometry by establishing linkage between algebra and geometry. He studied the mechanics of motion of a body and was the first to maintain that a body moves perpetually unless an external force stops it or changes its direction of motion. This would seem equivalent to the first law of motion.

      The list of his books runs to 200 or so, very few of which have survived. Even his monumental treatise on optics survived through its Latin translation. During the Middle Ages his books on cosmology were translated into Latin, Hebrew and other languages. He has also written on the subject of evolution, a book that deserves serious attention even today. In his writing, one can see a clear development of the scientific methods as developed and applied by the Muslims and comprising the systematic observation of physical phenomena and their linking together into a scientific theory. This was a major breakthrough in scientific methodology, as distinct from guess and gesture, and placed scientific pursuits on a sound foundation comprising systematic relationship between observation, hypothesis and verification.

      Ibn al-Haitham's influence on physical sciences in general, and optics in particular, has been held in high esteem and, in fact, it ushered in a new era in optical research, both in theory and practice.

Alhazen (c. 965 A.D. - c. 1039; Iraq)

Alhazen is regarded as being one of the greatest Islamic scientists during the medieval period and has been credited as being the first person to give an accurate description of how humans see. Although he was born in Iraq, Alhazen moved to Egypt between 996 and 1021and remained there until his death in 1039.

Alhazen's greatest contribution to the field of physics was his work entitled, Optics, in which Alhazen took Euclid's and Ptolemy's doctrines on visual rays and replaced them with his own belief that vision was the result of light coming from an object and moving into the eye. Alhazen thought that rays reached the surface of the eye perpendicularly and the combined effects from the perpendicular rays formed the image of the object. This hypothesis was based on Alhazen's theory that all objects reflected light in every direction.

All of the observations and experiments used in his work related to the camera obscura, perception, visual illusions, reflection and refraction and were heavily based upon mathematics. In regard to his work on refraction, Alhazen wrote in his book that refraction explained twilight. Alhazen stated that twilight was due to the refraction of the sun's rays in the earth's atmosphere. During his work on Optics, which was translated into Latin in 1270, Alhazen developed a problem, which involved curved mirrors and reflected light. Alhazen was able to solve this problem, which bears his name, for spherical mirrors through the method of intersecting a circle and hyperbola.

During his career, Alhazen was able to publish his theories on refraction, reflection, focusing with lenses, binocular vision, parabolic and spherical mirrors, spherical aberration, the rainbow, atmospheric refraction as well as astronomy. With regards to astronomy, Alhazen thought that there was an increase in the size of the heavenly bodies when they were near the earth's horizon. Alhazen also devised a system of physical spheres, which he arranged in such a way that made them responsible for the motions of the heavenly bodies

Moslem Opticians 

The Muslim Optician

BASRA- One of the many gifted and renowned Muslim scientists was Abu Ali Hasan Ibn al-Haitham, or Alhazen, born in Basra (present day Iraq) in 965AD. An eminent physician, he made his mark as the “father of modern optics.”

He conducted experiments on the propagation of light and color, optic illusions, as well as reflections. He also conducted the first experiments on the dispersion of light into its constituent colors. He came very close to developing a theory on magnifying lenses- which was in fact developed three centuries later in Italy- when he carried out experiments with glass vessels filled with water.

He wrote a book titled “Kitab al- Manazar” which was translated into Latin. It dealt in detail with the theory of rainbows, shadows, eclipses, and the physical nature of light.

All the medievel western writers on optics based their work on Alhazen’s theories. This Muslim optician also influenced Leonardo da Vinci and Johann Kepler.

Alhazen was the first to describe accurately the parts of the eye and provide scientific explanations for the process of vision. He explained binocular vision and correctly explained the apparent increase in size of the sun and moon when near the horizon.

He wrote more than 200 books, few of which have survived. But his contributions have been immense. Alhazen’s ideas brought forth a new era in theoretical and experimental optical research.

Al-Haitham is best known as Alhazen and is remembered for Alhazen's problem:

Given a light source and a spherical mirror, find the point on the mirror were the light would be reflected to the eye of an observer.

The problem leads to a quadratic, which was solved, with Greek style geometry. Al-Haitham had a less than satisfactory solution, Huygens found a good solution which  Vincenzo Riccati and Saladini simplified and improved.

Al-Haitham wrote a treatise on optics Kitab al-manazir, translated into Latin as Optical thesaurus Alhazen (1270). He worked on reflection, refraction, lenses, parabolic and spherical mirrors, spherical aberration and atmospheric refraction. He wrote on these topics after experimenting with lenses and mirrors.

His study of magnification with lenses led him to conclude that the magnification was caused by the curvature of the lens. He gave the first correct explanation of vision showing that light is reflected from an object into the eye.

His study of refraction led him to propose that the atmosphere had a finite depth of about 15 km. He explained twilight by refraction of sunlight once the Sun was less than 19 below the horizon. His studies of optics led him to propose the use of a camera obscura, and he was the first person to mention it.