Photography Is A Technique Of Producing Permanent Images On Sensitized

Photography is a technique of producing permanent images on sensitized surfaces by means of the photochemical action of light or other forms of radiant energy. In today's society, photography plays important roles as an information medium, as a tool in science and technology, and as an art form, and it is also a popular hobby. It is essential at every level of business and industry, being used in advertising, documentation, photojournalism, and many other ways. Scientific research, ranging from the study of outer space to the study of the world of subatomic particles, relies heavily on photography as a tool. In the 19th century, photography was the domain of a few professionals because it required large cameras and glass photographic plates. During the first decades of the 20th century, however, with the introduction of roll film and the box camera, it came within the reach of the public as a whole. Today the industry offers amateur and professional photographers a large variety of cameras and accessories. See also Motion Picture. The Camera and Its Accessories Modern cameras operate on the basic principle of the camera obscura (see Historical Development, below). Light passing through a tiny hole, or aperture, into an otherwise lightproof box casts an image on the surface opposite the aperture. The addition of a lens sharpens the image, and film makes possible a fixed, reproducible image. The camera is the mechanism by which film can be exposed in a controlled manner. Although they differ in structural details, modern cameras consist of four basic components: body, shutter, diaphragm, and lens. Located in the body is a lightproof chamber in which film is held and exposed. Also in the body, located opposite the film and behind the lens, are the diaphragm and shutter. The lens, which is affixed to the front of the body, is actually a grouping of optical glass lenses. Housed in a metal ring or cylinder, it allows the photographer to focus an image on the film. The lens may be fixed in place or set in a movable mount. Objects located at variou s distances from the camera can be brought into sharp focus by adjusting the distance between the lens and the film. The diaphragm, a circular aperture behind the lens, operates in conjunction with the shutter to admit light into the lighttight chamber. This opening may be fixed, as in many amateur cameras, or it may be adjustable. Adjustable diaphragms are composed of overlapping strips of metal or plastic that, when spread apart, form an opening of the same diameter as the lens; when meshed together, they form a small opening behind the center of the lens. The aperture openings correspond to numerical settings, called f-stops, on the camera or the lens. The shutter, a spring-activated mechanical device, keeps light from entering the camera except during the interval of exposure. Most modern cameras have focal-plane or leaf shutters. Some older amateur cameras use a drop-blade shutter, consisting of a hinged piece that, when released, pulls across the diaphragm opening and exposes the film for about 1/30th of a second. In the leaf shutter, at the moment of exposure, a cluster of meshed blades springs apart to uncover the full lens aperture and then springs shut. The focal-plane shutter consists of a black shade with a variable-size slit across its width. When released, the shade moves quickly across the film, exposing it progressively as the slit moves. Most modern cameras also have some sort of viewing system or viewfinder to enable the photographer to see, through the lens of the camera, the scene being photographed. Single-lens reflex cameras all incorporate this design feature, and almost all general-use cameras have some form of focusing system as well as a film-advance mechanism. Camera Designs Cameras come in a variety of configurations and sizes. The first cameras, ?pinhole? cameras, had no lens. The flow of light was controlled simply by blocking the pinhole. The first camera in general use, the box camera, consists of a wooden or plastic box with a simple lens and a drop-blade shutter at one end and a holder for roll film at the other. The box camera is equipped with a simple viewfinder that shows the extent of the picture area. Some

Avogadros Law Example Problem

Avogadros Law Example Problem Avogadros gas law states the volume of a gas is proportional to the number of moles of gas present when the temperature and pressure are held constant. This example problem demonstrates how to use Avogadros law to determine the volume of a gas when more gas is added to the system. Avogadro's Law Equation Before you can solve any problem regarding Avogadros gas law, its important to review the equation for this law. There are a few ways to write this  gas law, which is a mathematical relation. It may be stated: k V/n Here, k is a proportionality constant, V is the volume of a gas, and n is the number of moles of a gas. Avogadros law also means the ideal gas constant is the same value for all gases, so: constant p1V1/T1n1   P2V2/T2n2V1/n1   V2/n2V​1n2   V2n1 where p is pressure of a gas, V is volume, T is temperature, and n is number of moles. Avogadro's Law Problem A 6.0 L sample at 25 °C and 2.00 atm of pressure contains 0.5 mole of a gas. If an additional 0.25 mole of gas at the same pressure and temperature are added, what is the final total volume of the gas? Solution First, express Avogadros law by its  formula: Vi/ni Vf/nfwhereVi initial volumeni initial number of molesVf final volumenf final number of moles For this example, Vi 6.0 L and ni 0.5 mole. When 0.25 mole is added: nf ni 0.25 molenf 0.5 mole 0.25 molenf 0.75 mole The only variable remaining is the final volume. Vi/ni Vf/nf Solve for Vf Vf ​ Vinf/niV​f (6.0 L x 0.75 mole)/0.5 moleVf 4.5 L/0.5 Vf 9 L Check to see if the answer makes sense. You would expect the volume to increase if more gas is added. Is the final volume greater than the initial volume? Yes. Doing this check is useful because it is easy to put the initial number of moles in the numerator and the final number of moles in the denominator. If this had happened, the final volume answer would have been smaller than the initial volume. Thus, the final volume of the gas is 9.0 Notes Regarding Avogadro's Law Unlike Avogadros number, Avogadros law was actually proposed by   Amedeo Avogadro. In 1811, he hypothesized two samples of an ideal gas with the same volume and at the same pressure and temperature contained the same number of molecules.Avogadros law is also called Avogadros principle or Avogadros hypothesis.Like the other ideal gas laws, Avogadros law only approximates the behavior of real gases. Under conditions of high temperature or pressure, the law is inaccurate. The relation works best for gases held at low pressure and ordinary temperatures. Also, smaller gas particles- helium, hydrogen, and nitrogen- yield better results than larger molecules, which are more likely to interact with each other.Another mathematical relation used to express Avogadros law is: V/n k Here, V is the volume, n is the number of moles of the gas, and k is the proportionality constant. Its important to note this means the ideal gas constant is the same for all gases.