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This article is about the physicist. For the physician, see Ali ibn Sahl Rabban al-Tabari
Ali ibn Sahl Rabban al-Tabari

Abu al-Hasan Ali ibn Sahl Rabban al-Tabari was a Muslim Hakim , Ulema, Islamic medicine and Early Muslim sociology of Persian Jews or Zoroastrian descent, who produced the first encyclopedia of medicine....
. For the poet, see Ibn Sahl of Sevilla
Ibn Sahl of Sevilla

Ibn Sahl of Seville is considered one of the greatest Moorish poets of Andalusia of the 13th century.Ibn Sahl was born in 1212-3 in a Jewish family in Seville....
.

Ibn Sahl (Abu Sa`d al-`Ala' ibn Sahl) (c. 940-1000) was an Arabian mathematician
Islamic mathematics

Mathematics in medieval Islam or sometimes referred to as Islamic mathematics is a term used in the history of mathematics that refers to the mathematics developed in the Muslim world between 622 and 1600, in the part of the world where Islam was the dominant religion....
, physicist
Islamic physics

Islamic physics refers to the study of physics within Islamic science, which flourished during the Islamic Golden Age, variously dated from the 8th century to the 16th century, when experimental physics, mathematical physics and theoretical physics were studied in the Muslim world....
 and optics
Optics

Optics is the study of the behavior and properties of light including its optical phenomena with matter and its imaging by optical instruments....
 engineer
Inventions in the Islamic world

A significant number of inventions were developed in the medieval Muslim world, a geopolitical region that has at various times extended from Al-Andalus and Africa in the west to the Indian subcontinent and Malay Archipelago in the east....
 of the Islamic Golden Age
Islamic Golden Age

The Islamic Golden Age, also sometimes known as the Islamic Renaissance, was traditionally dated from the 700 A.D. to 1200 A.D.Common Era, but has been extended to the 15th and 16th centuries by some scholars....
 associated with the Abbasid
Abbasid

The Abbasid Caliphate was the third of the Islamic Caliphates of the Islamic Empire. The Caliphate is one of the high points of Islam, and at the time Muslim civilization, together with that of Byzantium, China and India, was the most developed part of the world....
 court of Baghdad
Baghdad

Baghdad is the Capital of Iraq and of Baghdad Governorate, with which it is also coterminous. With a municipal population estimated at 6.5 million, it is the largest city in Iraq, and the second largest city in the Arab World....
. Ibn Sahl's 984 treatise On Burning Mirrors and Lenses sets out his understanding of how curved mirror
Curved mirror

A curved mirror is a mirror with a curved reflective surface, which may be either convex or concave . Most curved mirrors have surfaces that are shaped like part of a sphere, but other shapes are sometimes used in optical devices....
s and lenses
Lens (optics)

A lens is an optics device with perfect or approximate axial symmetry which transmittance and refraction light, converging or diverging the beam....
 bend and focus light. Ibn Sahl is credited with first discovering the law of refraction
Refraction

Refraction is the change in direction of a wave due to a change in its speed. This is most commonly observed when a wave passes from one optical medium to another....
, usually called Snell's law
Snell's law

In optics and physics, Snell's law , is a mathematical formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves, passing through a boundary between two different isotropic medium , such as water and glass....
.






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This article is about the physicist. For the physician, see Ali ibn Sahl Rabban al-Tabari
Ali ibn Sahl Rabban al-Tabari

Abu al-Hasan Ali ibn Sahl Rabban al-Tabari was a Muslim Hakim , Ulema, Islamic medicine and Early Muslim sociology of Persian Jews or Zoroastrian descent, who produced the first encyclopedia of medicine....
. For the poet, see Ibn Sahl of Sevilla
Ibn Sahl of Sevilla

Ibn Sahl of Seville is considered one of the greatest Moorish poets of Andalusia of the 13th century.Ibn Sahl was born in 1212-3 in a Jewish family in Seville....
.

Ibn Sahl (Abu Sa`d al-`Ala' ibn Sahl) (c. 940-1000) was an Arabian mathematician
Islamic mathematics

Mathematics in medieval Islam or sometimes referred to as Islamic mathematics is a term used in the history of mathematics that refers to the mathematics developed in the Muslim world between 622 and 1600, in the part of the world where Islam was the dominant religion....
, physicist
Islamic physics

Islamic physics refers to the study of physics within Islamic science, which flourished during the Islamic Golden Age, variously dated from the 8th century to the 16th century, when experimental physics, mathematical physics and theoretical physics were studied in the Muslim world....
 and optics
Optics

Optics is the study of the behavior and properties of light including its optical phenomena with matter and its imaging by optical instruments....
 engineer
Inventions in the Islamic world

A significant number of inventions were developed in the medieval Muslim world, a geopolitical region that has at various times extended from Al-Andalus and Africa in the west to the Indian subcontinent and Malay Archipelago in the east....
 of the Islamic Golden Age
Islamic Golden Age

The Islamic Golden Age, also sometimes known as the Islamic Renaissance, was traditionally dated from the 700 A.D. to 1200 A.D.Common Era, but has been extended to the 15th and 16th centuries by some scholars....
 associated with the Abbasid
Abbasid

The Abbasid Caliphate was the third of the Islamic Caliphates of the Islamic Empire. The Caliphate is one of the high points of Islam, and at the time Muslim civilization, together with that of Byzantium, China and India, was the most developed part of the world....
 court of Baghdad
Baghdad

Baghdad is the Capital of Iraq and of Baghdad Governorate, with which it is also coterminous. With a municipal population estimated at 6.5 million, it is the largest city in Iraq, and the second largest city in the Arab World....
. Ibn Sahl's 984 treatise On Burning Mirrors and Lenses sets out his understanding of how curved mirror
Curved mirror

A curved mirror is a mirror with a curved reflective surface, which may be either convex or concave . Most curved mirrors have surfaces that are shaped like part of a sphere, but other shapes are sometimes used in optical devices....
s and lenses
Lens (optics)

A lens is an optics device with perfect or approximate axial symmetry which transmittance and refraction light, converging or diverging the beam....
 bend and focus light. Ibn Sahl is credited with first discovering the law of refraction
Refraction

Refraction is the change in direction of a wave due to a change in its speed. This is most commonly observed when a wave passes from one optical medium to another....
, usually called Snell's law
Snell's law

In optics and physics, Snell's law , is a mathematical formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves, passing through a boundary between two different isotropic medium , such as water and glass....
. He used the law of refraction to derive lens shapes that focus light with no geometric aberrations, known as anaclastic lenses.

In the reproduction of the figure from Ibn Sahl's manuscript, the critical part is the right-angled triangle
Triangle

A triangle is one of the basic shapes of geometry: a polygon with three corners or wikt:vertex and three sides or edges which are line segments....
. The inner hypotenuse
Hypotenuse

File:Triangle Sides.svgA hypotenuse is the longest side of a right triangle, the side opposite the right angle. The length of the hypotenuse of a right triangle can be found using the Pythagorean theorem, which states that the Square of the length of the hypotenuse equals the sum of the squares of the lengths of the other two sides....
 shows the path of an incident ray and the outer hypotenuse shows an extension of the path of the refracted ray if the incident ray met a crystal
Crystal

A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions....
 whose face is vertical at the point where the two hypotenuses intersect. According to Rashed, the ratio of the length of the smaller hypotenuse to the larger is the reciprocal
Reciprocal

Reciprocal may refer to:*Multiplicative inverse, in mathematics, the number 1/x, which multiplied by x'' gives the product 1, also known as a reciprocal...
 of the refractive index
Refractive index

The refractive index of a medium is a measure for how much the speed of light is reduced inside the medium. For example, typical soda-lime glass has a refractive index of 1.5, which means that in glass, light travels at times the speed of light in a vacuum....
 of the crystal.

The lower part of the figure shows a representation of a plano-convex lens (at the right) and its principal axis (the intersecting horizontal line). The curvature of the convex part of the lens brings all rays parallel to the horizontal axis (and approaching the lens from the right) to a focal point
Focal point

A focal point may mean:* Focus , the point at which initially collimated rays of light meet after passing through a convex lens, or reflecting off of a concave mirror....
 on the axis at the left.

In the remaining parts of the treatise, Ibn Sahl dealt with parabolic mirrors, ellipsoidal mirrors, biconvex lenses, and techniques for drawing hyperbolic arcs.

Ibn Sahl's treatise was used by Ibn al-Haitham
Ibn al-Haitham

, was an Arab or Persian people polymath. He made significant contributions to the principles of optics, as well as to anatomy, Islamic astronomy, Muslim inventions, Islamic mathematics, Islamic medicine, Ophthalmology in medieval Islam, Early Islamic philosophy, Islamic physics, Muslim psychology, visual perception, and to Islamic science...
 (965–1039), one of the greatest Arabic scholars of optics. In modern times, Rashed found the manuscript to have been dispersed over two libraries. He reassembled it, translated it, and published it.

See also

  • History of optics
    History of optics

    Optics began with the development of Lens by the ancient Egyptians and Mesopotamians, followed by theories on light and Visual perception developed by ancient Greek philosophy and Indian philosophy philosophers, and the development of geometrical optics in the Greco-Roman world....
  • Islamic science
    Islamic science

    Science in medival Islam, also known as Islamic science, is a term used in the history of science to refer to the science developed in the Muslim world between 7th and 16th centuries, a period also known as the Islamic Golden Age....
  • List of Arab scientists and scholars
    List of Arab scientists and scholars

    This is a list of scientists and scholars from the Arab World and Islamic Spain that lived from Ancient history up until the beginning of the Modern era, consisting primarily of scholars during the Middle Ages....


External links