Tanqih al-manazir: a revision of the Book of Optics and an explanation of the rainbow
The Persian scholar Kamal al-Din al-Farisi studied in Tabriz under Qutb al-Din Shirazi, who advised him to work through Ibn al-Haytham's Book of Optics. Out of this grew the Tanqih al-manazir (Revision of the Optics), a critical revision of the treatise with commentary and experiments of his own.
Its best-known part is the explanation of the rainbow. Al-Farisi modelled a raindrop with a water-filled glass sphere in a camera obscura and showed that the primary bow arises from two refractions and one reflection inside the drop. Almost at the same time Theodoric of Freiberg gave the same explanation in Europe; no Latin translation of al-Farisi is known, and no direct link between the two explanations has been established.
It shows Ibn al-Haytham's 'experiment as argument' still at work three hundred years later.
Why this date
disputed. The completion of the Tanqih is placed anywhere from before 1290 (Nazif) to after 1302 but before the death of Qutb al-Din Shirazi in 1311.
What it grew from
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Book of Optics and experiment as argument
improved · Confidence: high
Al-Farisi's Tanqih is essentially a revision of Ibn al-Haytham's Book of Optics, written after a deep study of it.
Link sources
- O'Connor J. J., Robertson E. F. «Kamal al-Din Abu'l Hasan Muhammad Al-Farisi», MacTutor History of Mathematics Verified 4 Oct 2026
Al-Shirazi advised him to consult the Optics of ibn al-Haytham and al-Farisi made such a deep study of this treatise that al-Shirazi suggested that he write what is essentially a revision of that major work.
- Russell G. A. «Fāresī, Kamāl-al-Dīn», Encyclopaedia Iranica, vol. IX, fasc. 3, 1999 (1999) Verified 4 Oct 2026
critical revision of Ebn al-Hayṯam’s Ketāb al-manāẓer
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.
- O'Connor J. J., Robertson E. F. «Kamal al-Din Abu'l Hasan Muhammad Al-Farisi», MacTutor History of Mathematics Verified 4 Oct 2026
Node sources
- Russell G. A. «Fāresī, Kamāl-al-Dīn», Encyclopaedia Iranica, vol. IX, fasc. 3, 1999 (1999) Verified 4 Oct 2026
The completion date of the Tanqīḥ has been controversial, placed from sometime before 1290 C.E. (Nazīf) to after 1302 C.E. but before Qoṭb-al-Dīn Šīrāzī’s death in 710/1311
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.