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  • phosphorous pentoxide (chemical compound)

    phosphorite: …beds contain about 30 percent phosphorous pentoxide (P2O5) and constitute the primary source of raw materials for most of world’s production of phosphate fertilizers. Significant deposits of phosphorites in the United States include the Phosphoria Formation in Idaho and the Monterey Formation in California. Major deposits also occur in the…

  • phosphorus (chemical element)

    Phosphorus (P), nonmetallic chemical element of the nitrogen family (Group 15 [Va] of the periodic table) that at room temperature is a colourless, semitransparent, soft, waxy solid that glows in the dark. atomic number 15 atomic weight 30.9738 melting point (white) 44.1 °C (111.4 °F) boiling point

  • Phosphorus (Swedish periodical)

    Swedish literature: Romanticism: …such as Polyfem (1809–12) and Phosphorus (1810–13), led the attack on the traditional school. Per Daniel Amadeus Atterbom, the most gifted of the Forforister, or Phosphorists, wrote the poem “Prolog” (1810) for Phosphorus, revealing both his talent and his commitment to Romanticism.

  • Phosphorus (classical mythology)

    Lucifer, (Latin: Lightbearer) in classical mythology, the morning star (i.e., the planet Venus at dawn); personified as a male figure bearing a torch, Lucifer had almost no legend, but in poetry he was often herald of the dawn. In Christian times Lucifer came to be regarded as the name of Satan

  • phosphorus compound, organic (chemical compound)

    insecticide: Organophosphates: The organophosphates are now the largest and most versatile class of insecticides. Two widely used compounds in this class are parathion and malathion; others are Diazinon, naled, methyl parathion, and dichlorvos. They are especially effective against sucking insects such as aphids and mites, which…

  • phosphorus cycle

    Phosphorus cycle, circulation of phosphorus in various forms through nature. Of all the elements recycled in the biosphere, phosphorus is the scarcest and therefore the one most limiting in any given ecological system. It is indispensable to life, being intimately involved in energy transfer and in

  • phosphorus deficiency (medical disorder)

    Phosphorus deficiency, condition in which phosphorus is insufficient or is not utilized properly. Phosphorus is a mineral that is vitally important to the normal metabolism of numerous compounds and (in solution) an acid that, with sulfur, must be neutralized by the base-forming ions of sodium,

  • phosphorus match (chemistry)

    match: …heat is a compound of phosphorus. This substance is found in the head of strike-anywhere matches and in the striking surface of safety matches.

  • phosphorus oxide

    oxide: Oxides of phosphorus: Phosphorus forms two common oxides, phosphorus(III) oxide (or tetraphosphorus hexoxide), P4O6, and phosphorus(V) oxide (or tetraphosphorus decaoxide), P4O10. Both oxides have a structure based on the tetrahedral structure of elemental white phosphorus. Phosphorus(III) oxide is a white crystalline

  • phosphorus pentoxide (chemical compound)

    nitrile: …formed by heating amides with phosphorous pentoxide. They can be reduced to primary amines through the action of lithium aluminum hydride or hydrolyzed to carboxylic acids in the presence of either an acid or a base.

  • phosphorus ylide (chemical compound)

    organosulfur compound: Sulfonium and oxosulfonium salts; sulfur ylides: …sulfur ylides, by analogy with phosphorus ylides employed in the Wittig reaction. The structures of sulfonium ylides and oxosulfonium ylides are analogous to those of sulfoxides and sulfones, respectively. Stabilization of the negative charge on carbon is primarily due to the high polarizability of sulfur. While phosphorus ylides react with…

  • phosphorus(III) oxide (chemical compound)

    oxide: Oxides of phosphorus: …common oxides, phosphorus(III) oxide (or tetraphosphorus hexoxide), P4O6, and phosphorus(V) oxide (or tetraphosphorus decaoxide), P4O10. Both oxides have a structure based on the tetrahedral structure of elemental white phosphorus. Phosphorus(III) oxide is a white crystalline solid that smells like garlic and has a poisonous vapour. It oxidizes slowly in air…

  • phosphorus(V) oxide (chemical compound)

    nitrile: …formed by heating amides with phosphorous pentoxide. They can be reduced to primary amines through the action of lithium aluminum hydride or hydrolyzed to carboxylic acids in the presence of either an acid or a base.

  • phosphorus-32 (chemical isotope)

    radioactivity: In medicine: Phosphorus-32 is useful in the identification of malignant tumours because cancerous cells tend to accumulate phosphates more than normal cells do. Technetium-99m, used with radiographic scanning devices, is valuable for studying the anatomic structure of organs.

  • phosphorus-rich phosphide (chemical compound)

    phosphide: …the basis of stoichiometry: (1) phosphorus-rich phosphides, in which the metal-to-phosphorus ratio is less than one, (2) metal-rich phosphides, where the metal-to-phosphorus ratio is greater than one, and (3) monophosphides, in which the metal-to-phosphorus ratio is exactly one. Phosphorus-rich phosphides tend to have lower thermal stabilities and lower melting points…

  • phosphorylase (enzyme)

    muscle disease: Indications of muscle disease: …the absence of the enzyme phosphorylase. Abnormal accumulations of glycogen are distributed within muscle cells. Symptoms of the condition include pain, stiffness, and weakness in the muscles on exertion. McArdle disease usually begins in childhood. No specific treatment is available, and persons affected are usually required to restrict exertion to…

  • phosphorylation (chemical reaction)

    Phosphorylation, in chemistry, the addition of a phosphoryl group (PO32-) to an organic compound. The process by which much of the energy in foods is conserved and made available to the cell is called oxidative phosphorylation (see cellular respiration). The process by which green plants convert

  • phosphorylcreatine (chemical compound)

    muscle: Energy stores: …the reactions of compounds called phosphagens. All of these compounds contain phosphorus in a chemical unit called a phosphoryl group, which they transfer to ADP to produce ATP (these compounds are also referred to as high-energy phosphates).

  • Phothisarat (king of Lan Xang)

    Photisarath, ruler (1520–47) of the Lao kingdom of Lan Xang whose territorial expansion embroiled Laos in the warfare that swept mainland Southeast Asia in the latter half of the 16th century. Photisarath was a pious Buddhist who worked to undermine animism and Brahmanic religious practices and

  • Phothisarath (king of Lan Xang)

    Photisarath, ruler (1520–47) of the Lao kingdom of Lan Xang whose territorial expansion embroiled Laos in the warfare that swept mainland Southeast Asia in the latter half of the 16th century. Photisarath was a pious Buddhist who worked to undermine animism and Brahmanic religious practices and

  • Photian Schism (Christianity)

    Photian Schism, a 9th-century-ad controversy between Eastern and Western Christianity that was precipitated by the opposition of the Roman pope to the appointment by the Byzantine emperor Michael III of the lay scholar Photius to the patriarchate of Constantinople. The controversy also involved

  • photic zone (oceanography)

    Photic zone, surface layer of the ocean that receives sunlight. The uppermost 80 m (260 feet) or more of the ocean, which is sufficiently illuminated to permit photosynthesis by phytoplankton and plants, is called the euphotic zone. Sunlight insufficient for photosynthesis illuminates the

  • photino (physics)

    supersymmetry: …fermionic supersymmetric partners, called the photino and the gluino. There has been no experimental evidence that such “superparticles” exist. If they do indeed exist, their masses could be in the range of 50 to 1,000 times that of the proton.

  • Photinus (firefly genus)

    aggressive mimicry: …the fireflies of the genus Photinus; the unlucky Photinus males deceived by the mimics are eaten. Another example is found in the brood parasitism practiced by the European cuckoo (Cuculus canorus). The eggs of this species closely resemble those of several kinds of small birds, in whose nests the cuckoo…

  • Photinus pyralis (firefly)

    bioluminescence: The role of bioluminescence in behaviour: In Photinus pyralis, a common North American firefly, the male flashes spontaneously while in flight, emitting on average a 0.3-second flash every 5.5 seconds if the temperature is 25 °C (77 °F). The females watch from the ground and wait for a male to flash. Upon…

  • Photisarath (king of Lan Xang)

    Photisarath, ruler (1520–47) of the Lao kingdom of Lan Xang whose territorial expansion embroiled Laos in the warfare that swept mainland Southeast Asia in the latter half of the 16th century. Photisarath was a pious Buddhist who worked to undermine animism and Brahmanic religious practices and

  • Photius, Saint (patriarch of Constantinople)

    Saint Photius, ; feast day February 6), patriarch of Constantinople (858–867 and 877–886), defender of the autonomous traditions of his church against Rome and leading figure of the 9th-century Byzantine renascence. Photius was related through his father to Tarasius, a civil servant who was

  • photo diode (electronics)

    radiation measurement: Conversion of light to charge: …solid-state device known as a photodiode. A device of this type consists of a thin semiconductor wafer that converts the incident light photons into electron-hole pairs. As many as 80 or 90 percent of the light photons will undergo this process, and so the equivalent quantum efficiency is considerably higher…

  • Photo League (American organization)

    Photo League, organization of New York City photographers devoted to documenting life in the city’s working-class neighbourhoods. The Photo League grew out of the Film and Photo League, a left-leaning organization started in the early 1930s whose goal was to document the class struggles in the

  • photo magazine (periodical)

    history of photography: Photojournalism: …1928–29 two of the largest picture magazines in Europe, the Münchner Illustrierte Presse and the Berliner Illustrirte Zeitung, began to print the new style of photographs. Erich Salomon captured revealing candid portraits of politicians and other personalities by sneaking his camera into places and meetings officially closed to photographers.

  • photo-drawing (art)

    Gyorgy Kepes: …made prints he called “photo-drawings,” in which he applied paint to a glass plate that he then used as though it were a negative.

  • photo-essay (photography)

    Margaret Bourke-White: …went on assignments to create photo-essays in Germany and the Soviet Union, as well as the Dust Bowl in the American Midwest. Those experiences allowed her to refine the dramatic style she had used in industrial and architectural subjects. Those projects also introduced people and social issues as subject matter…

  • photo-finish (sports)

    Olympic Games: Los Angeles, California, U.S., 1932: Uniform automatic timing and the photo-finish camera were used for the first time at the 1932 Games.

  • photo-ionization (physics)

    Photo-ionization, the interaction of electromagnetic radiation with matter resulting in the dissociation of that matter into electrically charged particles. The simplest example, the photoelectric effect (q.v.), occurs when light shines on a piece of metal, causing the ejection of electrons.

  • photo-organotroph (biology)

    nutrition: Nutritional patterns in the living world: …for this purpose are called photoorganotrophs. Animals, according to this classification, are chemoorganotrophs; i.e., they utilize chemical compounds to supply energy and organic compounds as electron donors.

  • photo-organotrophy (biology)

    nutrition: Nutritional patterns in the living world: …for this purpose are called photoorganotrophs. Animals, according to this classification, are chemoorganotrophs; i.e., they utilize chemical compounds to supply energy and organic compounds as electron donors.

  • Photo-realism (art)

    Photo-realism, American art movement that began in the 1960s, taking photography as its inspiration. Photo-realist painters created highly illusionistic images that referred not to nature but to the reproduced image. Artists such as Richard Estes, Ralph Goings, Audrey Flack, Robert Bechtle, and

  • photo-roman (photography and literature)

    French literature: Prose fiction: …writing joined to produce the photo-roman, concerned with exploring the relationship between the image, especially images of the body, and the narrative work that goes into its construction and interpretation. Good examples of the photo-roman are Barthes’s La Chambre Claire (1980; Camera Lucida) and Hervé Guibert’s Vice (1991). Gay writing,…

  • Photo-Secession (American society)

    Photo-Secession, the first influential group of American photographers that worked to have photography accepted as a fine art. Led by Alfred Stieglitz, the group also included Edward Steichen, Clarence H. White, Gertrude Käsebier, and Alvin Langdon Coburn. These photographers broke away from the

  • photo-text (photography)

    Lorna Simpson: …what became her signature technique: photo-text, which involved including brief passages of text that were often superimposed on the photographs and introduced new levels of meaning to the images. The images themselves were now posed studio shots, characterized by the use of human subjects, usually African American women, whose faces…

  • photoacoustic spectroscopy (chemistry)

    chemical analysis: Ultraviolet-visible spectrophotometry: …the technique is known as photoacoustic, or optoacoustic, spectrometry. Photoacoustic spectrometers typically employ microphones or piezoelectric transducers as detectors. Pressure waves result when the analyte expands and contracts as it absorbs chopped electromagnetic radiation.

  • photoactive compound (materials science)

    materials science: Photoresist films: A photoresist typically contains a photoactive compound (PAC) and an alkaline-soluble resin. The PAC, mixed into the resin, renders it insoluble. This mixture is coated onto the semiconductor wafer and is then exposed to radiation through a “mask” that carries the desired pattern. Exposed PAC is converted into an acid…

  • photoautotroph (biology)

    bacteria: Phototrophic metabolism: Life on Earth is dependent on the conversion of solar energy to cellular energy by the process of photosynthesis. The general process of photosynthesis makes use of pigments called chlorophylls that absorb light energy from the Sun and release an electron with a…

  • photoautotrophy (biology)

    bacteria: Phototrophic metabolism: Life on Earth is dependent on the conversion of solar energy to cellular energy by the process of photosynthesis. The general process of photosynthesis makes use of pigments called chlorophylls that absorb light energy from the Sun and release an electron with a…

  • photocatalyst (chemistry)

    Fujishima Akira: …titanium dioxide, acts as a photocatalyst—a substance that facilitates a chemical reaction when it is exposed to sunlight. In their experiments titanium dioxide exposed to light caused water to decompose, producing hydrogen and oxygen. This discovery gained worldwide attention as the “Honda-Fujishima effect” after it was reported in a 1972…

  • photocathode (electronics)

    Photocathode, an element of a photoelectric cell (q.v.) that emits electrons when struck by light, making possible the flow of electric current through the device. A substance often used for photocathodes is a partially oxidized silver–cesium

  • photocell (electronics)

    seawater: Optical properties: A photocell may be lowered into the ocean to measure light intensity at discrete depths and to determine light reduction from the surface value or from the previous depth value. The photocell may sense all available wavelengths or may be equipped with filters that pass only…

  • photochemical equivalence law (chemistry)

    Photochemical equivalence law, fundamental principle relating to chemical reactions induced by light, which states that for every quantum of radiation that is absorbed, one molecule of the substance reacts. A quantum is a unit of electromagnetic radiation with energy equal to the product of a

  • photochemical machining (machine tool technology)

    machine tool: Photochemical machining (PCM): PCM is an extension of CHM that uses a series of photographic and chemical etching techniques to produce components and devices in a wide range of metals, especially stainless steel.

  • photochemical reaction (chemical reaction)

    Photochemical reaction, a chemical reaction initiated by the absorption of energy in the form of light. The consequence of molecules’ absorbing light is the creation of transient excited states whose chemical and physical properties differ greatly from the original molecules. These new chemical

  • photochemical smog (atmospheric science)

    smog: Photochemical smog, which is also known as “Los Angeles smog,” occurs most prominently in urban areas that have large numbers of automobiles. It requires neither smoke nor fog. This type of smog has its origin in the nitrogen oxides and hydrocarbon vapours emitted by automobiles…

  • photochemistry

    radiation: Photochemistry: There are two “laws” of photochemistry. The first, the Grotthuss–Draper law (named for the chemists Christian J.D.T. von Grotthuss and John W. Draper), is simply: for light to produce an effect upon matter it must be absorbed. The second, or Stark–Einstein law (for the…

  • photochromatic interval (physiology)

    human eye: Scotopic sensitivity curve: …chromatic threshold, is called the photochromatic interval. This suggests that the rods give only achromatic, or colourless, vision, and that it is the cones that permit wavelength discrimination. The photochromatic interval for long wavelengths (red light) is about zero, which means that the intensity required to reach the sensation of…

  • photochrome (photography)

    history of photography: Early attempts at colour: In the 1880s photochromes, colour prints made from hand-coloured photographs, became fashionable, and they remained popular until they were gradually replaced in the first decades of the 20th century by Autochrome plates.

  • photochromic glass (chemistry)

    industrial glass: Photosensitivity: Traditional photochromic eyeglasses are generally alkali boroaluminosilicates with 0.01 to 0.1 percent silver halide and a small amount of copper. Upon absorption of light, the silver ion reduces to metallic silver, which nucleates to form colloids about 120 angstroms in size. This is small enough to…

  • photochromic system (chemistry)

    technology of photography: Photochromic systems: Certain dyelike substances can exist in a colourless and a coloured state. They are called photochromic compounds. The coloured state is formed by exposure to radiations of a certain wavelength. The compound reverts to its colourless state either in the dark or on…

  • photocoagulation (medicine)

    eye disease: Diabetes: Various types of laser photocoagulation of the retina are used in certain forms of diabetic retinopathy in an attempt to halt or slow its progression. In cases of retinal detachment or persistent or recurrent hemorrhage within the vitreous gel, more extensive surgical treatments are employed. Glaucoma stemming from diabetic…

  • photocollography (printing process)

    Collotype, photomechanical printing process that gives accurate reproduction because no halftone screen is employed to break the images into dots. In the process, a plate (aluminum, glass, cellophane, etc.) is coated with a light-sensitive gelatin solution and exposed to light through a p

  • photocomposition (printing)

    Photocomposition, method of assembling or setting type by photographing characters on film from which printing plates are made. The characters are developed as photographic positives on film or light-sensitive paper from a negative master containing all the characters; the film, carrying the

  • photoconductive cell (electronics)

    seawater: Optical properties: A photocell may be lowered into the ocean to measure light intensity at discrete depths and to determine light reduction from the surface value or from the previous depth value. The photocell may sense all available wavelengths or may be equipped with filters that pass only…

  • photoconductive exposure meter (photography)

    exposure meter: …of the variable resistance, or photoconductive, type. In those meters the light-sensitive element, sometimes a cadmium sulfide cell but most often consisting of silicon photodiodes, is connected to a battery-powered circuit and changes its electrical resistance with variations in the light intensity. The change in current is measured by a…

  • photoconductivity (physics)

    Photoconductivity, the increase in the electrical conductivity of certain materials when they are exposed to light of sufficient energy. Photoconductivity serves as a tool to understand the internal processes in these materials, and it is also widely used to detect the presence of light and measure

  • photocopier

    Photocopying machine, any device for producing copies of text or graphic material by the use of light, heat, chemicals, or electrostatic charges. The need for a process other than wet photographic reproduction for copying documents stimulated the invention of various techniques, notably the d

  • photocopying machine

    Photocopying machine, any device for producing copies of text or graphic material by the use of light, heat, chemicals, or electrostatic charges. The need for a process other than wet photographic reproduction for copying documents stimulated the invention of various techniques, notably the d

  • Photocorynus spiniceps (fish)

    sex: Courtship: The small angler fish (Photocorynus spiniceps) that cruise around at great depths are most unlikely to meet a member of the opposite sex at a time or place when the female happens to be ready to shed her eggs. As a form of insurance to this end, however, any…

  • photodamage (biochemistry)

    photochemical reaction: Photosensitization: …light-induced bleaching (one kind of photodamage) can be observed in nearly any coloured material left in sunlight. In fact, the photosynthetic systems in plants must be continuously dismantled, repaired, and rebuilt because of photodamage (primarily from singlet molecular oxygen).

  • photodetector (instrument)

    fax: Standard fax transmission: …solid-state scanner that has 1,728 photosensors in a single row. Each photosensor in turn generates a low or high variation in voltage, depending on whether the scanned spot is black or white. Since there normally are 4 scan lines per mm (100 scan lines per inch), the scanning of a…

  • photodiode (electronics)

    radiation measurement: Conversion of light to charge: …solid-state device known as a photodiode. A device of this type consists of a thin semiconductor wafer that converts the incident light photons into electron-hole pairs. As many as 80 or 90 percent of the light photons will undergo this process, and so the equivalent quantum efficiency is considerably higher…

  • photodisintegration (physics)

    Photodisintegration, in physics, nuclear reaction in which the absorption of high-energy electromagnetic radiation (a gamma-ray photon) causes the absorbing nucleus to change to another species by ejecting a subatomic particle, such as a proton, neutron, or alpha particle. For example, m

  • photodissociation (chemical reaction)

    ocean: Origin of the ocean waters: Photodissociation (i.e., separation due to the energy of light) of water vapour into molecular hydrogen (H2) and molecular oxygen (O2) in the upper atmosphere allowed the hydrogen to escape and led to a progressive increase of the partial pressure of oxygen at Earth’s surface. The…

  • photodynamic therapy (medicine)

    therapeutics: Photodynamic therapy: Another form of nonionizing radiation therapy is photodynamic therapy (PDT). This technique involves administering a light-absorbing substance that is selectively retained by the tumour cells. The cells are killed by exposure to intense light, usually laser beams of appropriate wavelengths. Lesions amenable to…

  • photodynamism (biology)

    Photodynamism, conversion of certain substances in the skin of animals into other substances by the action of light. The resultant compounds may be beneficial (e.g., vitamin D), but in some cases they produce disorders of the skin. The original compound may be present in normal skin; it may be

  • photoelasticity (optics)

    Photoelasticity, the property of some transparent materials, such as glass or plastic, while under stress, to become doubly refracting (i.e., a ray of light will split into two rays at entry). When photoelastic materials are subjected to pressure, internal strains develop that can be observed in

  • photoelectric absorption (physics)

    radiation measurement: Photoelectric absorption: In this process, the incident X-ray or gamma-ray photon interacts with an atom of the absorbing material, and the photon completely disappears; its energy is transferred to one of the orbital electrons of the atom. Because this energy in general far exceeds the…

  • photoelectric cell (electronics)

    Photoelectric cell, an electron tube with a photosensitive cathode that emits electrons when illuminated and an anode for collecting the emitted electrons. Various cathode materials are sensitive to specific spectral regions, such as ultraviolet, infrared, or visible light. The voltage between the

  • photoelectric colorimeter (instrument)

    colorimetry: …the instrument is called a photoelectric colorimeter.

  • photoelectric conductivity (physics)

    Photoconductivity, the increase in the electrical conductivity of certain materials when they are exposed to light of sufficient energy. Photoconductivity serves as a tool to understand the internal processes in these materials, and it is also widely used to detect the presence of light and measure

  • photoelectric diode tube (electronics)

    Photoelectric cell, an electron tube with a photosensitive cathode that emits electrons when illuminated and an anode for collecting the emitted electrons. Various cathode materials are sensitive to specific spectral regions, such as ultraviolet, infrared, or visible light. The voltage between the

  • photoelectric effect (physics)

    Photoelectric effect, phenomenon in which electrically charged particles are released from or within a material when it absorbs electromagnetic radiation. The effect is often defined as the ejection of electrons from a metal plate when light falls on it. In a broader definition, the radiant energy

  • photoelectric photometry (astronomy)

    photometry: …use of the more accurate photoelectric, rather than photographic, detectors. The faintest stars observed with photoelectric tubes had magnitudes of about 24. In photoelectric photometry, the image of a single star is passed through a small diaphragm in the focal plane of the telescope. After further passing through an appropriate…

  • photoelectric threshold frequency (physics)

    radiation: The photoelectric effect: The photoelectric threshold frequency, symbolized by the Greek letter nu with subscript zero, ν0, is that frequency at which the effect is barely possible; it is given by the ratio of the work function symbolized by the Greek letter psi, ψ, to Planck’s constant (ν0 =…

  • photoelectric tube (electronics)

    Photoelectric cell, an electron tube with a photosensitive cathode that emits electrons when illuminated and an anode for collecting the emitted electrons. Various cathode materials are sensitive to specific spectral regions, such as ultraviolet, infrared, or visible light. The voltage between the

  • photoelectric work function (physics)

    radiation: The photoelectric effect: …letter psi, ψ, called the photoelectric work function of the surface, must be supplied before the electron can be ejected. When a quantum of energy is greater than the work function, photoelectric emission is possible with the maximum energy symbolized by the Greek letter epsilon, ε, of the photoelectron (εmax)…

  • photoelectric yield (physics and electronics)

    radiation measurement: Scintillators: …fraction is known as the quantum efficiency of the light sensor. In a silicon photodiode, as many as 80 to 90 percent of the light photons are converted to electron-hole pairs, but in a photomultiplier tube, only about 25 percent of the photons are converted to photoelectrons at the wavelength…

  • photoelectron (physics)

    radiation measurement: Spectroscopy systems: …scintillation detector normally consists of photoelectrons in a photomultiplier tube. The average number produced by a 1-MeV particle is normally no more than a few thousand, and the observed energy resolution is typically 5–10 percent. In contrast, the same particle would produce several hundred thousand electron-hole pairs in a semiconductor,…

  • photoelectron spectroscopy

    spectroscopy: Photoelectron spectroscopy: Photoelectron spectroscopy is an extension of the photoelectric effect (see radiation: The photoelectric effect), first explained by Einstein in 1905, to atoms and molecules in all energy states. The technique involves the bombardment of a

  • photoemission (physics)

    Photoelectric effect, phenomenon in which electrically charged particles are released from or within a material when it absorbs electromagnetic radiation. The effect is often defined as the ejection of electrons from a metal plate when light falls on it. In a broader definition, the radiant energy

  • photoengraving (printing)

    Photoengraving, any of several processes for producing printing plates by photographic means. In general, a plate coated with a photosensitive substance is exposed to an image, usually on film; the plate is then treated in various ways, depending upon whether it is to be used in a relief

  • photofinishing laboratory (photography)

    technology of photography: The photography industry: Photofinishing laboratories process most amateur and some professional photographers’ films and prints. In the 1980s, virtually all of the total business of the laboratories in the United States was in colour processing.

  • photofission (physics)

    nuclear fission: Induced fission: …done by gamma-ray excitation (photofission) or through excitation of the nucleus by the capture of a neutron, proton, or other particle (particle-induced fission). The binding energy of a particular nucleon to a nucleus will depend on—in addition to the factors considered above—the odd–even character of the nucleus. Thus, if…

  • photogenic drawing (photography)

    William Henry Fox Talbot: These so-called photogenic drawings were basically contact prints on light-sensitive paper, which unfortunately produced dark and spotty images. In 1840 he modified and improved this process and called it the calotype (later the talbotype). Unlike the original process, it used a much shorter exposure time and a…

  • photogram (photographic print)

    Photogram, shadowlike photographic image made on paper without the use of a negative or a camera. It is made by placing objects between light-sensitive paper or film and a light source. Opaque objects lying directly on the paper produce a solid silhouette; transparent images or images that do not

  • photogrammetry (cartography)

    Photogrammetry, technique that uses photographs for mapmaking and surveying. As early as 1851 the French inventor Aimé Laussedat perceived the possibilities of the application of the newly invented camera to mapping, but it was not until 50 years later that the technique was successfully employed.

  • photograph

    history of photography: General considerations: of visual communication and expression, photography has distinct aesthetic capabilities. In order to understand them, one must first understand the characteristics of the process itself. One of the most important characteristics is immediacy. Usually, but not necessarily, the image that is recorded is formed by a lens in a camera.…

  • Photograph, The (novel by Lively)

    Penelope Lively: In The Photograph (2003) a man finds and investigates posthumous proof of his wife’s infidelity.

  • photographic emulsion

    Sir William de Wiveleslie Abney: …for his development of a photographic emulsion that he used to map the solar spectrum far into the infrared.

  • photographic film (photography)

    technology of photography: …scene being photographed onto a film coated with light-sensitive silver salts, such as silver bromide. A shutter built into the lens admits light reflected from the scene for a given time to produce an invisible but developable image in the sensitized layer, thus exposing the film.

  • photographic filter (optics and photography)

    Filter, in photography, device used to selectively modify the component wavelengths of mixed (e.g., white) light before it strikes the film. Filters may be made of coloured glass, plastic, gelatin, or sometimes a coloured liquid in a glass cell. They are most often placed over the camera lens but

  • photographic memory (psychology)

    memory abnormality: Hypermnesia: …memory, almost certainly eidetic (“photographic”) in nature. “S” also reported an unusual degree of synesthesia, though whether this helped or hindered his feats of memory is not clear. (A person shows signs of synesthesia when he reports that stimulation through one sense leads to experiences in another sense; for…

  • photographic photometry (astronomy)

    photometry: The fact that photographic plates are sensitive to violet and ultraviolet radiation, rather than to the green and yellow wavelengths to which the eye is most sensitive, led to the establishment of two separate magnitude scales, the visual and the photographic. The difference between the magnitudes given by…

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