Kamāl al-Dīn al-Fārisī

Infobox_Philosopher
region = Persian scholar
color = #B0C4DE

name = Fārisī
birth =
death =
school_tradition = Persian science

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Kamal al-Din Abu'l-Hasan Muhammad Al-Farisi (1267-ca.1319/1320 [Sameen Ahmed Khan, [http://www.osa-opn.org/Content/ViewFile.aspx?id=10890 "Arab Origins of the Discovery of the Refraction of Light"] , in "Optics and Photonics News", October 2007, pp. 22-23] ) ( _fa. كمال‌الدين ابوالحسن محمد فارسی) was a prominent Persian Muslim physicist, mathematician, and scientist born in Tabriz, Iran. He made two major contributions to science, one on optics, the other on number theory. Al-Farisi was a pupil of the great astronomer and mathematician Qutb al-Din al-Shirazi, who in turn was a pupil of Nasir al-Din Tusi.

Optics

His work on optics was prompted by a question put to him concerning the refraction of light. Shirazi advised him to consult the "Book of Optics" of Ibn al-Haytham (Alhacen), and al-Farisi made such a deep study of this treatise that Shirazi suggested that he write what is essentially a revision of that major work, which came to be called the "Tanqih". Qutb al-Din Al-Shirazi himself was writing a commentary on works of Avicenna at the time.

Al-Farisi is known for giving the first mathematically satisfactory explanation of the rainbow. [cite web
author=O'Connor, J. J.; Robertson, E. F. | date=November 1999
url=http://www-gap.dcs.st-and.ac.uk/~history/Biographies/Al-Farisi.html
title=Kamal al-Din Abu'l Hasan Muhammad Al-Farisi
publisher=University of St. Andrews | accessdate=2007-06-07 ] His research in this regard was based on theoretical investigations in dioptrics conducted on the so-called "Burning Sphere" ("al-Kura al-muhriqa") in the tradition of Ibn Sahl (d. ca. 1000) and Ibn al-Haytham (d. ca. 1041) after him. As he noted in his "Kitab Tanqih al-Manazir" ("The Revision of the Optics"), al-Farisi used a large clear vessel of glass in the shape of a sphere, which was filled with water, in order to have an experimental large-scale model of a rain drop. He then placed this model within a camera obscura that has a controlled aperture for the introduction of light. He projected light unto the sphere and ultimately deducted through several trials and detailed observations of reflections and refractions of light that the colors of the rainbow are phenomena of the decomposition of light. His research had resonances with the studies of his contemporary Theodoric of Freiberg (without any contacts between them; even though they both relied on Ibn al-Haytham's legacy), and later with the experiments of Descartes and Newton in dioptrics (for instance, Newton conducted a similar experiment at Trinity College, though using a prism rather than a sphere). [ Nader El-Bizri, "Ibn al-Haytham", in "Medieval Science, Technology, and Medicine: An Encyclopedia", eds. Thomas F. Glick, Steven J. Livesey, and Faith Wallis (New York — London: Routledge, 2005), pp. 237-240. ] [ Nader El-Bizri, "Optics", in "Medieval Islamic Civilization: An Encyclopedia", ed. Josef W. Meri (New York – London: Routledge, 2005), Vol. II, pp. 578-580 ] [ Nader El-Bizri, "Al-Farisi, Kamal al-Din," in "The Biographical Encyclopaedia of Islamic Philosophy", ed. Oliver Leaman (London — New York: Thoemmes Continuum, 2006), Vol. I, pp. 131-135 ] [ Nader El-Bizri, "Ibn al-Haytham, al-Hasan", in "The Biographical Encyclopaedia of Islamic Philosophy", ed. Oliver Leaman (London — New York: Thoemmes Continuum, 2006), Vol. I, pp. 248-255.]

Number theory

Al-Farisi made a number of important contributions to number theory. His most impressive work in number theory is on amicable numbers. In "Tadhkira al-ahbab fi bayan al-tahabb" ("Memorandum for friends on the proof of amicability") introduced a major new approach to a whole area of number theory, introducing ideas concerning factorization and combinatorial methods. In fact al-Farisi's approach is based on the unique factorization of an integer into powers of prime numbers.

Notes

References

*
* 'R Rashed, The development of Arabic mathematics : between arithmetic and algebra (London, 1994).'
* 'R Rashed, Entre arithmétique et algèbre: Recherches sur l'histoire des mathématiques arabes (Paris, 1984).'
* 'A G Agargün and C R Fletcher, al-Farisi and the fundamental theorem of arithmetic, Historia Math. 21 (2) (1994), 162-173.'
* 'R Rashed, Materials for the study of the history of amicable numbers and combinatorial analysis (Arabic), J. Hist. Arabic Sci. 6 (1-2) (1982), 278-209.'
* 'R Rashed, Nombres amiables, parties aliquotes et nombres figurés aux XIIIème et XIVème siècles, Arch. Hist. Exact Sci. 28 (2) (1983), 107-147.'
* 'R Rashed, Le modèle de la sphère transparente et l'explication de l'arc-en-ciel : Ibn al-Haytham - al-Farisi, Revue d'histoire des sciences 22 (1970), 109-140.'