Kamāl al-Dīn al-Fārisī

Farisi is known for giving the first mathematically satisfactory explanation of the rainbow, and an explication of the nature of colours that reformed the theory of Ibn al-Haytham Alhazen.

[12] 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.

As he noted in his Kitab Tanqih al-Manazir (The Revision of the Optics), 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.

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).

1258) elaborated on this by stating that there are no less than five of such paths, via lemon (yellow), blood (red), pistachio (green), indigo (blue) and grey.

In fact Farisi's approach is based on the unique factorization of an integer into powers of prime numbers.

Kamal al-Din al-Farisi's autograph manuscript in Optics, Tanqih al-Manazir, 1309 A.D., Adilnor Collection.
Kamāl al-Dīn al-Fārisī: Primary and secondary rainbow construction, around 1300. From Revision of the Optics of Ibn al-Haytham (Tanqīḥ al-Manāẓir li-Ḏawī'l-Abṣār wa'l-Baṣāʾir). The point light source is on top. A partial explanation, with the rays in red and black producing the primary and secondary rainbow, respectively.
The colophone of Al-Basa'ir fi 'ilm al-Basa'ir, copied in 731 H.E. from Kamal al-Din's original manuscript, states that Kamal al-Din's real name is al-Hasan ibn Ali ibn al-Hasan and he has completed the work in 708 H.E. The scribe states also that Kamal al-Din died on 19 Dhu al-Qa'dah 718 H.E. (12 January 1319)