Optics
From the Quicksilver Metaweb.
This is a placeholder for Optics
Stephensonia
Isaac Newton sat on Opticks for 30 years waiting for Robert Hooke to die, so he could write him out of history; Newton's Rings were first described by Hooke.
Authored entries
Optics
There are three major branches of optics: 1. Geometrical optics deals with light as rays, traveling in ideal straight lines except when it is bent by reflection or refraction at a surface. 2. Physical optics deals with the nature and behavior of light as a wave. Physical optics reduces to geometric optics in the limit where the wavelength of light goes to zero. 3. Quantum optics deals with light as packets of energy -- photons -- which interact with matter at the level of individual atoms and molecules.
Basic principles of optics describe what light is and how it behaves. To study visible light, scientists use a prism (wedge of glass) that produces a band of colors called the visible spectrum. Scientists analyze this and other spectra with an instrument called a spectroscope.
A number of different reactions may occur when light strikes the surface of an object. Diffraction, interference, reflection, and refraction are some of the basic principles that describe what may happen. Other principles include the chemical effects of light, dispersion, the photoelectric effect, and polarization.
Optics is the branch of physics and engineering that is concerned with the properties of light. It describes how light is produced, how it is transmitted, and how it can be detected, measured, and used. Optics includes the study of visible light and of infrared and ultraviolet rays, both of which are invisible. Many instruments, including binoculars, cameras, magnifiers, microscopes, projectors, and telescopes, operate according to the principles of optics. All these instruments have optical devices, such as lenses and mirrors, which transmit and control light. Light is detected and measured with instruments called light meters. * a Light meter is an instrument used to measure the brightness of light. Light meters serve a variety of specialized needs. Astronomers use them to measure the brightness of stars. Lighting engineers use them to measure the brightness of lighting in homes and offices. Photographers use light meters to measure the intensity of the light in scenes they wish to photograph.
Most light meters include a photo cell made of cadmium sulfide or gallium arsenide. A less sensitive type of light meter uses a cell of selenium. When light shines on it, the cell produces a small voltage, which is measured by a voltage meter. The voltage increases with the brightness of the light. The brightness of light can be expressed in terms of foot-candles, lumens, luxes, or other units. Many photographers' meters measure brightness in arbitrary units chosen by the meter's manufacturer. The units correspond to exposure settings that are on a photographer's camera.
Scientists have used the principles of optics to increase the number of ways to use light. For example, they can transmit light along a twisted or curved path by sending the light through a filament called an optical fiber. Scientists use a device called a laser as an important and powerful light source.
Lasers
A laser is a device that produces a very narrow, powerful beam of light. Some beams are thin enough to drill 200 holes on a spot as tiny as the head of a pin. The ability to focus laser light so precisely makes it extremely powerful. For example, some beams can pierce a diamond, the hardest natural substance. Others can trigger a small nuclear reaction. A laser beam also can be transmitted over long distances with no loss of power. Some beams have reflected off the moon and returned to the earth.
The special qualities of laser light make it ideal for a variety of applications. Some types of lasers, for example, are used to play music, read price codes, cut and weld metal, and transmit information. Lasers can also guide a missile to a target, repair damaged eyes, and produce spectacular displays of light. Still other lasers are used to align walls and ceilings in a building or to print documents. Some lasers even can detect the slightest movement of a continent.
Lasers vary greatly in size. A typical laser has three main parts. These parts are (1) an energy source, (2) a substance called an active medium, and (3) a structure enclosing the active medium known as an optical cavity. The energy source supplies an electric current, light, or other form of energy. The atoms of the active medium can absorb the energy, store it for a while, and release the energy as light. Some of this light triggers other atoms to release their energy. More light is added to the triggering light. Mirrors at the ends of the optical cavity reflect the light back into the active medium. The reflected light causes more atoms to give off light. The light grows stronger, and part of it emerges from the laser as a narrow beam. Some beams are visible. Others consist of invisible forms of radiation.
There are four main kinds of lasers. They are solid-state lasers, semiconductor lasers, gas lasers, and dye lasers. Advances in laser technology and uses have soared since the early 1970's. Today, the enormous information-carrying capacity of optical fibers is opening a new era in home entertainment, communication, and computer technology. Even so, researchers remain convinced that the most exciting and revolutionary uses of lasers still lie ahead.
History of Optics
The development of optics began chiefly during the 1600's. The Italian scientist Galileo Galilei built telescopes to observe the planets and the stars. Sir Isaac Newton, experimented with lenses and used a prism to break sunlight into its colors. In Holland, the physicist Christiaan Huygens studied polarization and proposed a wave theory of light.
During the early 1800's, two physicists, Thomas Young and Augustin Fresnel, did much to confirm Huygens' theory. Young formulated the principle of the interference of light. Fresnel then developed a mathematical formula that supported this principle. Most scientists accepted the work of Young and Fresnel as proof of Huygens' theory.
During the mid-1800's, accurate measurements of the speed of light were made by the scientists Armand H. L. Fizeau and Jean B. L. Foucault. At about the same time, two scientists, Robert Bunsen and Gustav Kirchhoff, showed that atoms of chemical elements produced the color bands of the spectrum. In 1864, the physicist James C. Maxwell introduced the electromagnetic theory of light.
Scientists made several important discoveries in optics during the late 1800's and the 1900's. Such scientists as Albert A. Michelson, Frits Zernike, and Dennis Gabor received the Nobel Prize for physics for their work in optics.