Kamal al-Din al-Farisi

Kamal al-Din al-Hasan ibn Ali al-Farisi was born in Tabriz and studied under the great astronomer Qutb al-Din al-Shirazi at the Maragheh Observatory. Shirazi encouraged him to study the monumental Book of Optics by Ibn al-Haytham (Alhazen), leading Farisi to write Tanqih al-Manazir (The Revision of the Optics).

Farisi made groundbreaking discoveries in physics, constructing an experimental camera obscura and a water-filled glass sphere to simulate a raindrop. He correctly proved that the primary rainbow is caused by two refractions and one internal reflection of sunlight inside a water droplet, simultaneous with and independent of Theodoric of Freiberg in Europe.