Absorption bandAccording to quantum mechanics, atoms and molecules can only hold certain defined quantities of energy, or exist in specific states. When such quanta of electromagnetic radiation are emitted or absorbed by an atom or molecule, energy of the radiation changes the state of the atom or molecule from an initial state to a final state. An absorption band is a range of wavelengths, frequencies or energies in the electromagnetic spectrum which are characteristic of a particular transition from initial to final state in a substance.
Balmer seriesThe Balmer series, or Balmer lines in atomic physics, is one of a set of six named series describing the spectral line emissions of the hydrogen atom. The Balmer series is calculated using the Balmer formula, an empirical equation discovered by Johann Balmer in 1885. The visible spectrum of light from hydrogen displays four wavelengths, 410 nm, 434 nm, 486 nm, and 656 nm, that correspond to emissions of photons by electrons in excited states transitioning to the quantum level described by the principal quantum number n equals 2.
Ancient Roman units of measurementThe ancient Roman units of measurement were primarily founded on the Hellenic system, which in turn was influenced by the Egyptian and the Mesopotamian systems. The Roman units were comparatively consistent and well documented. The basic unit of Roman linear measurement was the pes or Roman foot (plural: pedes). Investigation of its relation to the English foot goes back at least to 1647, when John Greaves published his Discourse on the Romane foot.
Extinction (astronomy)In astronomy, extinction is the absorption and scattering of electromagnetic radiation by dust and gas between an emitting astronomical object and the observer. Interstellar extinction was first documented as such in 1930 by Robert Julius Trumpler. However, its effects had been noted in 1847 by Friedrich Georg Wilhelm von Struve, and its effect on the colors of stars had been observed by a number of individuals who did not connect it with the general presence of galactic dust.
Ultraviolet catastropheThe ultraviolet catastrophe, also called the Rayleigh–Jeans catastrophe, was the prediction of late 19th century/early 20th century classical physics that an ideal black body at thermal equilibrium would emit an unbounded quantity of energy as wavelength decreased into the ultraviolet range.The term "ultraviolet catastrophe" was first used in 1911 by Paul Ehrenfest, but the concept originated with the 1900 statistical derivation of the Rayleigh–Jeans law.
Extreme ultravioletExtreme ultraviolet radiation (EUV or XUV) or high-energy ultraviolet radiation is electromagnetic radiation in the part of the electromagnetic spectrum spanning wavelengths shorter that the hydrogen Lyman-alpha line from 121 nm down to the X-ray band of 10 nm, and therefore (by the Planck–Einstein equation) having photons with energies from 10.26 eV up to 124.24 eV. EUV is naturally generated by the solar corona and artificially by plasma, high harmonic generation sources and synchrotron light sources.
Lead smeltingPlants for the production of lead are generally referred to as lead smelters. Primary lead production begins with sintering. Concentrated lead ore is fed into a sintering machine with iron, silica, limestone fluxes, coke, soda ash, pyrite, zinc, caustics or pollution control particulates. Smelting uses suitable reducing substances that will combine with those oxidizing elements to free the metal. Reduction is the final, high-temperature step in smelting. It is here that the oxide becomes the elemental metal.
Lead poisoningLead poisoning, also known as plumbism and saturnism, is a type of metal poisoning caused by lead in the body. Symptoms may include abdominal pain, constipation, headaches, irritability, memory problems, infertility, and tingling in the hands and feet. It causes almost 10% of intellectual disability of otherwise unknown cause and can result in behavioral problems. Some of the effects are permanent. In severe cases, anemia, seizures, coma, or death may occur. Exposure to lead can occur by contaminated air, water, dust, food, or consumer products.
Lead glassLead glass, commonly called crystal, is a variety of glass in which lead replaces the calcium content of a typical potash glass. Lead glass contains typically 18–40% (by mass) lead(II) oxide (PbO), while modern lead crystal, historically also known as flint glass due to the original silica source, contains a minimum of 24% PbO. Lead glass is often desirable for a variety of uses due to its clarity. In marketing terms it is often called crystal glass.
White leadWhite lead is the basic lead carbonate 2PbCO3·Pb(OH)2. It is a complex salt, containing both carbonate and hydroxide ions. White lead occurs naturally as a mineral, in which context it is known as hydrocerussite, a hydrate of cerussite. It was formerly used as an ingredient for lead paint and a cosmetic called Venetian ceruse, because of its opacity and the satiny smooth mixture it made with dryable oils. However, it tended to cause lead poisoning, and its use has been banned in most countries.
