Reproduction of a page of Ibn Sahl’s manuscript

The above image shows his discovery of the law of refraction. Ibn Sahl (c. 940-1000) was a Persian Mathematician in the court of Baghdad. About 984 he wrote a treatise On burning Mirrors and Lenses in which he set out his understanding of how mirrors and lenses bend and focus light. In his work he discovered a law of refraction. He used his law of refraction to compute the shapes of lenses and mirrors that focus light at a single point on the axis.

Mesopotamian seal showing a star, the Moon and the Pleiades cluster

The ancient Babylonians apparently used the telescope before Pythagoras’s time. Mesopotamian astronomers, like the one illustrated on the ancient seal above, cataloged the non-planetary fixed stars, observed and recorded their observations on occultations of the planets by the sun and moon, and determined correctly within a small fraction the length of the synodic revolution of the moon. Their long line of astronomical records on clay tablets stored in the British Museum, dating back to 747 B.C., indicate they observed some of the moons of Jupiter and Saturn.  “There is said to be distinct evidence that they observed the four satellites of Jupiter, and strong reason to believe that they were acquainted likewise with the seven satellites of Saturn,” wrote the English Orientalist George Rawlinson, in the 1860’s.  “It has generally been assumed that they were wholly ignorant of the telescope,” added the Camden professor of ancient history. “But if the satellites of Saturn are really mentioned, as it is thought that they are, upon some of the tablets, it will follow—strange as it may seem to us—that the Babylonians probably possessed optical instruments of the nature of telescopes, since it is impossible, even in the clear vapourless sky of Chaldea [ancient Babylonia], to discern the faint moons of that distant planet without lenses.”

Robert Hooke's Microscope

Advances in Lens technology led to startling scientific revelations such as the discovery of the cell by Robert Hooke in 1665. He examined (under a coarse, compound microscope) very thin slices of cork and saw a multitude of tiny pores that he remarked looked like the walled compartments a monk would live in. Because of this association, Hooke called them cells, the name they still bear.

Artists during this period were quick to make use of the benefits of this exciting new technology. In 1508 Leonardo da Vinci first described the principles of a camera obscura in his Codex Atlanticus.

The word optics is a derivative of the ancient Greek ὀπτική (optika), meaning appearance or look. The study of optics began with the development of the first lens in ancient Assyria which is located in Modern Day Iraq. This early invention was followed by theories of light and vision developed by ancient Greek and Indian Philosophers such as Euclid who in 300 B.C. noted that light appeared to travel at great speed in straight lines. In The Face of the Moon,  Plutarch claimed, “The moon is very uneven and rugged.”  How could he have determined this if the ancients were not using telescopes to observe its terrain at the time? In another of these passages, speaking of Pythagoras’s wisdom in the sixth century B.C., the ancient philosopher Iamblichus suggested that the Greeks used telescopes by spelling out the word when he announced, “Sight is made precise by the compass, rule, and telescope.”

Optics refers to the scientific study of the behavior and properties of light, and can be regarded as a sub-field of the broader study of electromagnetism. The field of optics covers a wide range of studies that can generally be separated into two basic fields. The pure science aspects of the field are often called optical science or optical physics. The Application of the optical sciences are referred to as optical engineering. Modern innovations in optical engineering are known as optoelectronics and photonics. Optical science covers many related disciplines including physics, psychology, anatomy opthomology, and optometry.

The Visby Viking Lens

Several 11th century hoards found at Viking sites on the island of Gotland, Sweden, contained biconvex lenses made from rock-crystal. Some of them were set in silver. A few lenses had an almost perfect elliptical shape. The symmetry of the lenses as well as their biconvex elliptical form and fine polish, which resulted in a very good imaging, made a sensation when discovered by modern scientists. The idea of producing at such an early date quality lenses that could be almost as accurate as those of modern optics, was something unheard of. After a series of tests it became clear that the quality of the 11th century rock-crystal lenses made on a turning lathe nearly equaled that of modern samples made with CNC machines 

As news trickled in to Europe about how the Lens worked as an optical instrument, europeans began to create lenses using glass. This modern fabrication method ushered in a great period of learning that we now know as the Renaisance. During this period, great strides were made to apply the use of these lenses to varying scientific instruments.

Replica of Galileo's Telescope

Galileo Galilei (1564 – 1642),was an Italian astronomer and philosopher who played a major role in the scientific revolution. His achievements were all based on his improvements to the telescope and consequent astronomical observations and support for Capernicus’ theory of heliocentrism. Galileo's championing of heliocentrism was controversial within his lifetime. The matter was investigated by the Roman Inquisition in 1615, and they concluded that it could be supported as only a possibility, not an established fact. Galileo later defended his views which appeared to attack those of the Pope. He was tried by the Inquisition, found "vehemently suspect of heresy", forced to recant, and spent the rest of his life under house arrest. It was while Galileo was under house arrest that he wrote one of his finest works, Two new Sciences.

From 1670 to 1672, Sir Isaac Newton lectured on optics. During this period he investigated the refraction of light, demonstrating that a prism could decompose white light into a spectrum of colors, and that a lens and a second prism could recompose the multicolored spectrum into white light.

Modern artist and theorist David Hockney, has speculated that Vermeer used a camera obscura to achieve precise positioning in his compositions, asserting that this view is supported by certain light and perspective effects. The often discussed sparkling pearly highlights in Vermeer's paintings have also been linked by advocates to the possible use of a camera obscura, the primitive lens of which would produce halation. 

The Electromagnetic Spectrum

The electromagnetic spectrum is a guage used to measure the range of all possible electromagnetic radiation frequencies. The “electromagnetic spectrum” of an object is the characteristic distribution of electromagnetic radiation from that particular object. The electromagnetic spectrum extends from below the frequencies used for modern radio (at the long-wavelength end) through gamma radiation (at the short-wavelength end), covering wavelengths from thousands of kilometers down to a fraction the size of an atom. The wavelengths travel at varying speeds from the speed of sound (640 MPH) to the speed of light (186,000 MPS). It is thought that the short wavelength limit is in the vicinity of the Planck length, and the long wavelength limit is the size of the universe itself, although in principle the spectrum is infinite and continuous.

Visible Light Spectrum
The visible spectrum is the portion of the electromagnetic spectrum that can be detected by the human eye. A typical human eye will respond to wavelengths in the vicinity of 400–790 terahertz. A light-adapted eye generally has its maximum sensitivity at around 540 THz. The spectrum does not, however, contain all the colors that the human eyes and brain can distinguish. Unsaturated colors such as pink, and purple colors such as magenta are absent, for example, because they can only be made by a mix of multiple wavelengths. The eyes of many species perceive wavelengths different from the spectrum visible to the human eye. For example, many insects, such as bees, can see light in the ultraviolet, which is useful for finding nectar in flowers. For this reason, plant species whose lifecycles are linked to insect pollination may owe their reproductive success to their appearance in ultraviolet light, rather than how colorful they appear to our eyes. Birds are also said to be able to see into the ultraviolet (300-400 nm) and oddly enough, the sex-dependent markings on some bird plumage is only visible in the ultraviolet range. Other animals, such as tropical fish and birds, have more complex color vision systems than humans. In the latter example, tetrachromacy is achieved through up to four cone types, depending on species. Brightly colored oil droplets inside the cones shift or narrow the spectral sensitivity of the cell. It has been suggested that it is likely that pigeons are pentachromats. Marine mammals have only a single cone type and are thus monochromats. Several marsupials such as the fat-tailed dunnart (Sminthopsis crassicaudata) have been shown to have trichromatic colour vision. Many invertebrates have color vision. Honey and bumblebees have trichromatic color vision, which is insensitive to red but sensitive in ultraviolet to a color called bee purple. Papilio butterflies apparently have tetrachromatic color vision despite possessing six photoreceptor types. The most complex color vision system in animal kingdom has been found in stomatopods with up to 12 different spectral receptor types which are thought to work as multiple dichromatic units. Perception of color is achieved in mammals through color receptors containing pigments with different spectral sensitivities. In most primates closely related to humans there are three types of color receptors (known as cone cells). This confers trichromatic color vision, so these primates, like humans, are known as trichromats. Many other primates and other mammals are dichromats, and many mammals have little or no color vision.The human eye can distinguish about 10 million different colors.