![]() The rise of modern, scientific optics occurred gradually during the late 1500s and early 1600s, a period when all areas of physical science were undergoing revolutionary changes. Modern cameras are miniature camera obscura, where instead of the image being traced by hand, it is recorded by an array of electronic components or a sheet of film coated with light-sensitive chemicals. The lens or pinhole projects an image of the outer world on the opposite interior wall of the dark room, where it can be traced on paper or simply viewed. A camera obscura is a darkened room pierced by a pinhole or a larger hole in which a convex lens is inserted. In the 1400s, the device known as the camera obscura, Latin for “dark chamber” and origin of the English word “camera,” became popular in Europe. The making and wearing of eyeglasses spread awareness of lenses and the ability to craft them over all Europe, preparing the way for other advances in optics. In the 1400s, the ability of concave lenses to correct nearsightedness was discovered by German churchman and scientist Nicholas of Cusa (1401–1464). Although expensive, eyeglasses gradually became common in some places. This changed with the invention of eyeglasses in Italy around 1280. Various properties of lenses and prisms were observed by Arab and European scientists in the Middle Ages-English scientist and Franciscan monk Roger Bacon (1215–1294) was the first person to write down observations on the magnifying properties of lenses and also wrote a book attempting to explain the nature of rainbows-but no general agreement was reached on the nature of light itself, and, apart from the use of lenses as burning-glasses to start fires, few practical uses were found for optics. ![]() Arab scientists such as Ibn Sahl (c.940–1000) and Ibn al Haitham (963–1039) published treatises on mirrors and lenses that would eventually influence European students of optics. Growth in optics was slow throughout the Middle Ages (AD 900–1400). Later, the Romans also used lenses as burning-glasses, though they do not seem to have understood their full potential. Greeks of the fifth century BC were able to make glass and understood the ability of lenses to concentrate sunlight to burning intensity. Aristotle (384–322 BC) denied Democritus's theory of atoms and void, and proposed a quite different theory of light, namely, that light is an alteration of the materials between the source of illumination and the eye. Pythagoras (c.575–500 BC) explained that light is not the cause of visual sensation, but that “seeing rays” are emitted from the eye, rays which interact with light somehow at the surface of the object being viewed or in some other way. The followers of Democritus (c.460–370 BC), who taught that the world was made of atoms and void (emptiness), speculated that light consisted of streams of particles and that visual sensation is caused when these particles strike the eye. They also knew that light rays are reflected from a surface at the same angle that they strike it. Greek philosophers reasoned from the casting of shadows by solid objects that light must travel in straight lines. The earliest known theories about the nature of light were made by the ancient Greeks. Historical Background and Scientific Foundations Optical systems have been essential to scientific and technological progress. Lenses, mirrors, lasers, and optical fibers are used in data transmission, storage, and retrieval in surgery weapons targeting document scanning and printing and for many other purposes. Especially through systems made of lenses-pieces of glass or plastic shaped to alter the light passing through them-optics have made possible photography the discovery of microorganisms through microscopes the correction of some vision disorders by eyeglasses and contact lenses the study of the distant universe through telescopes movie and slide projection and thousands of industrial processes, including the manufacture of computer microchips using optics to outline billions of transistors on tiny tiles of silicon. Optics is the branch of physics concerned with the nature and uses of light.
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