Abu Sad al-Ala ibn Sahl

Diagram from Ibn Sahl's handwriting showing the law of refraction at the top left (Rashed, 1990).

Abu Sad al-Ala ibn Sahl (short Ibn Sahl , Arabic ابن سهل ، أبو سعد العلاء, DMG Ibn Sahl, Abū Saʿd al-ʿAlāʾ ; * at 940; † around 1000) was a Persian mathematician and physicist who worked in Baghdad during the heyday of Islam during the Abbasid caliphate .

Life

Around 984 he wrote a treatise on burning mirrors and glasses , which contains the first known correct form of the law of refraction (see illustration on the right). [The time is derived from the dedication to the Buyiden ruler Samsam-o-dowleh, who ruled Baghdad from 983 to 987.]

Ibn Sahl's treatise was used by Alhazen but was then forgotten. The law was rediscovered in the 17th century by Thomas Harriot , Willebrord van Roijen Snell and René Descartes and is known today as Snellius' law of refraction .

It was not until 1990 that the historian Roshdi Rashed succeeded in reconstructing the treatise from two fragments kept in Damascus and Tehran.

literature

• Roshdi Rashed: A Pioneer in Anaclastics. Ibn Sahl on Burning Mirrors and Lenses. In: Isis , Volume 81, 1990, pp. 464-491 ( JSTOR 233423 )
• Roshdi Rashed: Géométrie et dioptrique au Xe siècle. Ibn Sahl, al-Quhi et Ibn al-Haytham . Les Belles Lettres, Paris 1993.
• Jim Al-Khalili: Pathfinders: The Golden Age of Arabic Science. Allen Lane, London 2010, ISBN 978-1-84614-161-4 .
• Jim Al-Khalili : The House of Wisdom . S. Fischer, 2011, ISBN 978-3-10-000424-6 , pp. 251 f .