Ibn Sahl (full name: ''Abū Saʿd al-ʿAlāʾ ibn Sahl'' ; c. 940–1000) was a

Persian Persian may refer to: * People and things from Iran, historically called ''Persia'' in the English language ** Persians, the majority ethnic group in Iran, not to be conflated with the Iranic peoples ** Persian language, an Iranian language of the ...

mathematician and

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate caus ...

of the

Islamic Golden Age The Islamic Golden Age was a period of cultural, economic, and scientific flourishing in the history of Islam, traditionally dated from the 8th century to the 14th century. This period is traditionally understood to have begun during the reign ...

, associated with the

Buyid The Buyid dynasty ( fa, آل بویه, Āl-e Būya), also spelled Buwayhid ( ar, البويهية, Al-Buwayhiyyah), was a Shia Iranian dynasty of Daylamite origin, which mainly ruled over Iraq and central and southern Iran from 934 to 1062. Coupl ...

court of

Baghdad Baghdad (; ar, بَغْدَاد , ) is the capital of Iraq and the second-largest city in the Arab world after Cairo. It is located on the Tigris near the ruins of the ancient city of Babylon and the Sassanid Persian capital of Ctesiphon ...

. Nothing in his name allows us to glimpse his country of origin. He is known to have written an optical treatise around 984. The text of this treatise was reconstructed by

Roshdi Rashed Roshdi Rashed (Arabic: رشدي راشد), born in Cairo in 1936, is a mathematician, philosopher and historian of science, whose work focuses largely on mathematics and physics of the medieval Arab world. His work explores and illuminates the unr ...

from two manuscripts (edited 1993).: Damascus, al-Ẓāhirīya MS 4871, 3 fols., and Tehran, Millī MS 867, 11 fols. The Tehran manuscript is much longer, but it is badly damaged, and the Damascus ms. contains a section missing entirely from the Tehran ms. The Damascus ms. has the title ''Fī al-'āla al-muḥriqa'' "On the burning instruments", the Tehran ms. has a title added in a later hand ''Kitāb al-harrāqāt'' "The book of burners". Ibn Sahl is the first Muslim scholar known to have studied

Ptolemy Claudius Ptolemy (; grc-gre, Πτολεμαῖος, ; la, Claudius Ptolemaeus; AD) was a mathematician, astronomer, astrologer, geographer, and music theorist, who wrote about a dozen scientific treatises, three of which were of importanc ...

's ''Optics'', and as such an important precursor to the ''

Book of Optics The ''Book of Optics'' ( ar, كتاب المناظر, Kitāb al-Manāẓir; la, De Aspectibus or ''Perspectiva''; it, Deli Aspecti) is a seven-volume treatise on optics and other fields of study composed by the medieval Arab scholar Ibn al- ...

'' by

Ibn Al-Haytham Ḥasan Ibn al-Haytham, Latinized as Alhazen (; full name ; ), was a medieval mathematician, astronomer, and physicist of the Islamic Golden Age from present-day Iraq.For the description of his main fields, see e.g. ("He is one of the prin ...

(Alhazen), written some thirty years later. Ibn Sahl dealt with the optical properties of

curved mirror A curved mirror is a mirror with a curved reflecting surface. The surface may be either ''convex'' (bulging outward) or ''concave'' (recessed inward). Most curved mirrors have surfaces that are shaped like part of a sphere, but other shapes are ...

s and

lenses A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

and has been described as a pioneer in the field of construction of

,different types of

mirrors A mirror or looking glass is an object that Reflection (physics), reflects an image. Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse the ...

, burning glasses, and studies of

glassmaking Glass production involves two main methods – the float glass process that produces sheet glass, and glassblowing that produces bottles and other containers. It has been done in a variety of ways during the history of glass. Glass container ...

. Ibn Sahl uses this law to derive lens shapes that focus light with no geometric aberrations, known as anaclastic lenses. In the remaining parts of the treatise, Ibn Sahl dealt with Reflective mirrors, ellipsoidal mirrors, burning glasses,

industry and techniques for drawing hyperbolic arcs. He also wrote about different methods of

glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of ...

production and manufacture of high quality colored glass. Ibn Sahl designed convex lenses that focus lights rays that are parallel, which can cause an object to burn at a specific distance. A biconvex lens has the ability to focus at a specific point at an infinite distance. Ibn Sahl has made many contributions to optics, he also wrote an article about the celestial sphere. A constant ratio is the main focus point of his study, and it allows for a better understanding of refraction lenses. Ibn Sahl did an experiment where a piece of crystal was used to propagate a ray of light through the crystal which then refracts in the air.

References

Sources

*Rashed, R. "A pioneer in anaclastics: Ibn Sahl on burning mirrors and lenses", ''

Isis Isis (; ''Ēse''; ; Meroitic: ''Wos'' 'a''or ''Wusa''; Phoenician: 𐤀𐤎, romanized: ʾs) was a major goddess in ancient Egyptian religion whose worship spread throughout the Greco-Roman world. Isis was first mentioned in the Old Kingd ...

'' 81, pp. 464–491, 1990. *Rashed, R., ''Géométrie et dioptrique au Xe siècle: Ibn Sahl, al-Quhi et Ibn al-Haytham.'' Paris: Les Belles Lettres, 1993 * *
PDF version
* * {{DEFAULTSORT:Sahl Mathematicians under the Buyid dynasty 10th-century Iranian mathematicians Medieval physicists 10th-century Iranian scientists History of optics 1000 deaths

See also

References

Sources