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Quantum Tunnelling
Quantum tunnelling, also known as tunneling ( US) is a quantum mechanical phenomenon whereby a wavefunction can propagate through a potential barrier. The transmission through the barrier can be finite and depends exponentially on the barrier height and barrier width. The wavefunction may disappear on one side and reappear on the other side. The wavefunction and its first derivative are continuous. In steady-state, the probability flux in the forward direction is spatially uniform. No particle or wave is lost. Tunneling occurs with barriers of thickness around 1–3 nm and smaller. Some authors also identify the mere penetration of the wavefunction into the barrier, without transmission on the other side as a tunneling effect. Quantum tunneling is not predicted by the laws of classical mechanics where surmounting a potential barrier requires sufficient kinetic energy. Quantum tunneling plays an essential role in physical phenomena such as nuclear fusion and alpha radioact ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American English
American English, sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United States. English is the Languages of the United States, most widely spoken language in the United States and in most circumstances is the de facto common language used in government, education and commerce. Since the 20th century, American English has become the most influential form of English worldwide. American English varieties include many patterns of pronunciation, vocabulary, grammar and particularly spelling that are unified nationwide but distinct from other English dialects around the world. Any North American English, American or Canadian accent (sociolinguistics), accent perceived as lacking noticeably local, ethnic or cultural markedness, markers is popularly called General American, "General" or "Standard" American, a fairly uniform dialect continuum, accent continuum native to certain regions of the U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Friedrich Hund
Friedrich Hermann Hund (4 February 1896 – 31 March 1997) was a German physicist from Karlsruhe known for his work on atoms and molecules. Scientific career Hund worked at the Universities of Rostock, Leipzig, Jena, Frankfurt am Main, and Göttingen. Hund worked with such prestigious physicists as Schrödinger, Dirac, Heisenberg, Max Born, and Walter Bothe. At that time, he was Born's assistant, working with quantum interpretation of band spectra of diatomic molecules. After his studies of mathematics, physics, and geography in Marburg and Göttingen, he worked as a private lecturer for theoretical physics in Göttingen (1925), professor in Rostock (1927), Leipzig University (1929), Jena (1946), Frankfurt/Main (1951) and from 1957 again in Göttingen. Additionally, he stayed in Copenhagen (1926) with Niels Bohr and lectured on the atom at Harvard University (1928). He published more than 250 papers and essays in total. Hund made pivotal contributions to quantum theory - esp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrodes
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials depending on the type of battery. The electrophore, invented by Johan Wilcke, was an early version of an electrode used to study static electricity. Anode and cathode in electrochemical cells Electrodes are an essential part of any battery. The first electrochemical battery made was devised by Alessandro Volta and was aptly named the Voltaic cell. This battery consisted of a stack of copper and zinc electrodes separated by brine-soaked paper disks. Due to fluctuation in the voltage provided by the voltaic cell it wasn't very practical. The first practical battery was invented in 1839 and named the Daniell cell after John Frederic Daniell. Still making use of the zinc–copper electrode combination. Since then many more batteries have be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Field Emission Current
Field electron emission, also known as field emission (FE) and electron field emission, is emission of electrons induced by an electrostatic field. The most common context is field emission from a solid surface into a vacuum. However, field emission can take place from solid or liquid surfaces, into a vacuum, a fluid (e.g. air), or any non-conducting or weakly conducting dielectric. The field-induced promotion of electrons from the valence to conduction band of semiconductors (the Zener effect) can also be regarded as a form of field emission. The terminology is historical because related phenomena of surface photoeffect, thermionic emission (or Richardson–Dushman effect) and "cold electronic emission", i.e. the emission of electrons in strong static (or quasi-static) electric fields, were discovered and studied independently from the 1880s to 1930s. When field emission is used without qualifiers it typically means "cold emission". Field emission in pure metals occurs in high e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galvanometer
A galvanometer is an electromechanical measuring instrument for electric current. Early galvanometers were uncalibrated, but improved versions, called ammeters, were calibrated and could measure the flow of current more precisely. A galvanometer works by deflecting a pointer in response to an electric current flowing through a coil in a constant magnetic field. Galvanometers can be thought of as a kind of actuator. Galvanometers came from the observation, first noted by Hans Christian Ørsted in 1820, that a magnetic compass's needle deflects when near a wire having electric current. They were the first instruments used to detect and measure small amounts of current. André-Marie Ampère, who gave mathematical expression to Ørsted's discovery, named the instrument after the Italian electricity researcher Luigi Galvani, who in 1791 discovered the principle of the frog galvanoscope – that electric current would make the legs of a dead frog jerk. Galvanometers have bee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Michelson Interferometer
The Michelson interferometer is a common configuration for optical interferometry and was invented by the 19/20th-century American physicist Albert Abraham Michelson. Using a beam splitter, a light source is split into two arms. Each of those light beams is reflected back toward the beamsplitter which then combines their amplitudes using the superposition principle. The resulting interference pattern that is not directed back toward the source is typically directed to some type of photoelectric detector or camera. For different applications of the interferometer, the two light paths can be with different lengths or incorporate optical elements or even materials under test. The Michelson interferometer (among other interferometer configurations) is employed in many scientific experiments and became well known for its use by Michelson and Edward Morley in the famous Michelson–Morley experiment (1887) in a configuration which would have detected the Earth's motion through the sup ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert Francis Earhart
The name Robert is an ancient Germanic given name, from Proto-Germanic "fame" and "bright" (''Hrōþiberhtaz''). Compare Old Dutch ''Robrecht'' and Old High German ''Hrodebert'' (a compound of '' Hruod'' ( non, Hróðr) "fame, glory, honour, praise, renown" and ''berht'' "bright, light, shining"). It is the second most frequently used given name of ancient Germanic origin. It is also in use as a surname. Another commonly used form of the name is Rupert. After becoming widely used in Continental Europe it entered England in its Old French form ''Robert'', where an Old English cognate form (''Hrēodbēorht'', ''Hrodberht'', ''Hrēodbēorð'', ''Hrœdbœrð'', ''Hrœdberð'', ''Hrōðberχtŕ'') had existed before the Norman Conquest. The feminine version is Roberta. The Italian, Portuguese, and Spanish form is Roberto. Robert is also a common name in many Germanic languages, including English, German, Dutch, Norwegian, Swedish, Scots, Danish, and Icelandic. It can be use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive. The term is also used more generally to characterize any type of exponential (or, rarely, non-exponential) decay. For example, the medical sciences refer to the biological half-life of drugs and other chemicals in the human body. The converse of half-life (in exponential growth) is doubling time. The original term, ''half-life period'', dating to Ernest Rutherford's discovery of the principle in 1907, was shortened to ''half-life'' in the early 1950s. Rutherford applied the principle of a radioactive element's half-life in studies of age determination of rocks by measuring the decay period of radium to lead-206. Half-life is constant over the lifetime of an exponentially decaying quantity, and it is a characteristic unit for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Friedrich Kohlrausch (physicist)
Friedrich Wilhelm Georg Kohlrausch (14 October 1840 – 17 January 1910) was a German physicist who investigated the conductive properties of electrolytes and contributed to knowledge of their behaviour. He also investigated elasticity, thermoelasticity, and thermal conduction as well as magnetic and electrical precision measurements. Nowadays, Friedrich Kohlrausch is classed as one of the most important experimental physicists. His early work helped to extend the absolute system of Carl Friedrich Gauss and Wilhelm Weber to include electrical and magnetic measuring units. Biography Education Son of Rudolf Kohlrausch, Friedrich Wilhelm Georg Kohlrausch was born on October 14, 1840, in Rinteln, Germany. After studying physics at Erlangen and Göttingen, Friedrich Kohlrausch completed his doctorate in Göttingen. Teaching After a two-year work as a lecturer in Frankfurt, Kohlrausch was appointed a professor of physics at the University of Göttingen (1866–70). During 1870 Koh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Egon Schweidler
Egon Schweidler, (* 10 February 1873, in Vienna; † 10 February 1948, in Salzburg Seeham) was an Austrian physicist. Biography He was born in 1873 as the son of the court and ''Gerichtsadvokaten'' Emil von Schweidler born in Vienna. After studying physics and mathematics, he earned his doctorate with a dissertation "On the internal friction of mercury and some Amalgamen" (1895). He was assistant to Franz Exner. Career In 1899, he went to the University of Vienna. In 1911 he was appointed as an associate professor. From 1911 to 1926, he was the head of the Department of Experimental Physics at the University of Innsbruck, where he was dean in 1924 and rector in 1925/26. In 1926, he returned as per his appeal as an Ordinary II at the Physics Institute of the University of Vienna. There, he also worked as a secretary (1929-1933), Secretary-General (1933-1938), and Vice President (1939-1945) of the Austrian Academy of Sciences. In 1933, he was also elected chairman of the German Phy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ernest Rutherford
Ernest Rutherford, 1st Baron Rutherford of Nelson, (30 August 1871 – 19 October 1937) was a New Zealand physicist who came to be known as the father of nuclear physics. ''Encyclopædia Britannica'' considers him to be the greatest experimentalist since Michael Faraday (1791–1867). Apart from his work in his homeland, he spent a substantial amount of his career abroad, in both Canada and the United Kingdom. In early work, Rutherford discovered the concept of radioactive half-life, the radioactive element radon, and differentiated and named alpha and beta radiation. This work was performed at McGill University in Montreal, Quebec, Canada. It is the basis for the Nobel Prize in Chemistry he was awarded in 1908 "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances", for which he was the first Oceanian Nobel laureate, and the first to perform the awarded work in Canada. In 1904, he was elected as a member to the Am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
