Optics in the Golden Age

Throughout history, Islam has distinguished itself in many areas of science – one of them being optics, the study of the behavior and properties of light. One may assume that optics aren’t nearly as important as, for example, math, but you’d be surprised at what far-reaching advancements the Islamic Empire made – and how such developments led to the invention of modern day devices, such as the camera.

Before Muslim scientists took over the field of optics, it was believed that the eye is the source of light and that the world would be dark without it. There were also no viable explanations for colors at the time – imagine waking up to see every shade and hue under the sun and not being able to understand for yourself why you’re able to see them in the first place! Fortunately, the “Father of Optics” Ibn Al-Haytham began his studies and shed light upon (pun intended) the biggest ocular questions of that day.

Ibn Al-Haytham studied the structure of the eye and wrote a comprehensive work about his findings, titled Kitab Al-Manazir, or The Book of Optics. It contained a diagram of the eye and its connection to the central nervous system, an observation that had never been previously made. He is the one who named the parts of the eye, and their English translations are still used today: retina, cornea, vitreous humor, and aqueous humor. Also, due to his understanding of the eye and its processes, he studied light and proposed his own theories about colors and light refraction. He also denied the apocryphal belief that light travels into the eyes from external objects to create images. Those discoveries alone were enough to give him his title, but they didn’t stop there. He came to the conclusion that light is all the same despite its source, and that it is a movement with variable speed – the beginning of the color theory.

Two centuries later, Qutb al-Din al-Shirazi expanded on Ibn Al-Haytham’s theories and gave the first correct explanation of the formation of a rainbow. Though little remains of his work, they survive him in his pupil Kamal al-Din al-Farisi, who made a major contribution to the field of optics. He was asked a question concerning the refraction of light, and his teacher al-Shirazi encouraged him to consult Al-Haytham’s work, which al-Farisi comprehensively studied. He helped to expand on the theory of rainbow formation; he proposed that the colors occurred because of the “superimposition of different forms of an image on a dark background.” In his notes, he wrote, “If the images then interpenetrate, the light is again intensified and produces a bright yellow. Next, the blended image diminishes and becomes a darker and darker red until it disappears when the sun is outside the cone of rays refracted after one reflection.” Our understanding of color truly began with those words.

The eye doctors of Islam were proficient and leading in the treatment of eye diseases. On top of Ibn al-Haytham, Qutb al-Din al-Shirazi, and Kamal al-Din al-Farisi’s discoveries, a man named Razi recognized the pupil’s reaction to the light and Ibn Sina described the number of inessential muscles of the eyeball (six). One of the most significant developments made in this area of medicine was discovered by Ammar bin Ali, who introduced a “hollow metallic needle” that aided in the extraction of cataracts – Europe began to use this method later in the 19th century.

Remarkably, some discoveries extend to modern day devices such as the camera. Ibn Al-Haytham investigated mirror theory, mirrors, light refraction, and how light passing through lens breaks down into the color spectrum. Such studies allowed for advancements in refining the shape of lenses; European scholars expanded on them and used them as a solid foundation for the development of lenses for telescopes, magnifying lenses, and eyeglasses.

Subhan’Allah! It really blows me away that we now understand the ‘hows’ and ‘whys’ of color, are safe from several eye diseases, and can use cameras with ease all thanks to the huge contributions of Islam.