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Heinrich Hertz
Heinrich Rudolf Hertz ( ; ; 22 February 1857 – 1 January 1894) was a German physicist who first conclusively proved the existence of the electromagnetic waves predicted by James Clerk Maxwell's equations of electromagnetism. The unit of frequency, cycle per second, was named the " hertz" in his honor.IEC History . Iec.ch. Biography Heinrich Rudolf Hertz was born in 1857 in Hamburg, then a sovereign state of the German Confederation, into a prosperous and cultured Hanseatic family. His father was |
Hamburg
Hamburg (, ; nds, label=Hamburg German, Low Saxon, Hamborg ), officially the Free and Hanseatic City of Hamburg (german: Freie und Hansestadt Hamburg; nds, label=Low Saxon, Friee un Hansestadt Hamborg),. is the List of cities in Germany by population, second-largest city in Germany after Berlin, as well as the overall List of cities in the European Union by population within city limits, 7th largest city and largest non-capital city in the European Union with a population of over 1.85 million. Hamburg's urban area has a population of around 2.5 million and is part of the Hamburg Metropolitan Region, which has a population of over 5.1 million people in total. The city lies on the River Elbe and two of its tributaries, the River Alster and the Bille (Elbe), River Bille. One of Germany's 16 States of Germany, federated states, Hamburg is surrounded by Schleswig-Holstein to the north and Lower Saxony to the south. The official name reflects History of Hamburg, Hamburg's history ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoelectric Effect
The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid state and quantum chemistry to draw inferences about the properties of atoms, molecules and solids. The effect has found use in electronic devices specialized for light detection and precisely timed electron emission. The experimental results disagree with classical electromagnetism, which predicts that continuous light waves transfer energy to electrons, which would then be emitted when they accumulate enough energy. An alteration in the intensity of light would theoretically change the kinetic energy of the emitted electrons, with sufficiently dim light resulting in a delayed emission. The experimental results instead show that electrons are dislodged only when the light exceeds a certain frequency—regardless of the light's intensity o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cycle Per Second
The cycle per second is a once-common English name for the unit of frequency now known as the hertz (Hz). The plural form was typically used, often written cycles per second, cycles/second, c.p.s., c/s, or, ambiguously, just cycles (Cy./Cyc.). The term comes from the fact that sound waves have a frequency measurable in their number of oscillations, or '' cycles'', per second. With the organization of the International System of Units in 1960, the cycle per second was officially replaced by the hertz, or reciprocal second, "s−1" or "1/s". Symbolically, "cycle per second" units are "cycle/second", while hertz is "Hz" or "s−1". For higher frequencies, ''kilocycles'' (kc), as an abbreviation of ''kilocycles per second'' were often used on components or devices. Other higher units like ''megacycle'' (Mc) and less commonly ''kilomegacycle'' (kMc) were used before 1960 and in some later documents. These have modern equivalents such as kilohertz (kHz), megahertz (MHz), and gigahertz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maxwell's Equations
Maxwell's equations, or Maxwell–Heaviside equations, are a set of coupled partial differential equations that, together with the Lorentz force law, form the foundation of classical electromagnetism, classical optics, and electric circuits. The equations provide a mathematical model for electric, optical, and radio technologies, such as power generation, electric motors, wireless communication, lenses, radar etc. They describe how electric and magnetic fields are generated by charges, currents, and changes of the fields.''Electric'' and ''magnetic'' fields, according to the theory of relativity, are the components of a single electromagnetic field. The equations are named after the physicist and mathematician James Clerk Maxwell, who, in 1861 and 1862, published an early form of the equations that included the Lorentz force law. Maxwell first used the equations to propose that light is an electromagnetic phenomenon. The modern form of the equations in their most common ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
James Clerk Maxwell
James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and scientist responsible for the classical theory of electromagnetic radiation, which was the first theory to describe electricity, magnetism and light as different manifestations of the same phenomenon. Maxwell's equations for electromagnetism have been called the " second great unification in physics" where the first one had been realised by Isaac Newton. With the publication of " A Dynamical Theory of the Electromagnetic Field" in 1865, Maxwell demonstrated that electric and magnetic fields travel through space as waves moving at the speed of light. He proposed that light is an undulation in the same medium that is the cause of electric and magnetic phenomena. (This article accompanied an 8 December 1864 presentation by Maxwell to the Royal Society. His statement that "light and magnetism are affections of the same substance" is at page 499.) The unification of light and elec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromagnetic Waves
In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays. All of these waves form part of the electromagnetic spectrum. Classically, electromagnetic radiation consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields. Depending on the frequency of oscillation, different wavelengths of electromagnetic spectrum are produced. In a vacuum, electromagnetic waves travel at the speed of light, commonly denoted ''c''. In homogeneous, isotropic media, the oscillations of the two fields are perpendicular to each other and perpendicular to the direction of energy and wave propagation, forming a transverse wave. The position of an electromagnetic wave within the electromagnetic spectrum can be characterized ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physicist
A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate causes of phenomena, and usually frame their understanding in mathematical terms. Physicists work across a wide range of research fields, spanning all length scales: from sub-atomic and particle physics, through biological physics, to cosmological length scales encompassing the universe as a whole. The field generally includes two types of physicists: experimental physicists who specialize in the observation of natural phenomena and the development and analysis of experiments, and theoretical physicists who specialize in mathematical modeling of physical systems to rationalize, explain and predict natural phenomena. Physicists can apply their knowledge towards solving practical problems or to developing new technologies (also known as a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rumford Medal
The Rumford Medal is an award bestowed by Britain's Royal Society every alternating year for "an outstandingly important recent discovery in the field of thermal or optical properties of matter made by a scientist working in Europe". First awarded during 1800, it was created after a 1796 donation of $5000 by the scientist Benjamin Thompson, known as Count Rumford, and is accompanied by a gift of £1000. Since its inception, the award has been granted to 104 scientists, including Rumford himself during 1800. It has been awarded to citizens of the United Kingdom sixty-one times, France fourteen times, Germany eight times, the Netherlands seven times, Sweden four times, the United States three times, Italy twice and once each to citizens of Australia, Hungary, Belgium, Luxembourg and New Zealand. List of recipients See also * List of physics awards This list of physics awards is an index to articles about notable awards for physics. The list includes lists of awards by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Matteucci Medal
The Matteucci Medal is an Italian award for physicists, named after Carlo Matteucci from Forlì. It was established to award physicists for their fundamental contributions. Under an Italian Royal Decree dated July 10, 1870, the Italian Society of Sciences was authorized to receive a donation from Carlo Matteucci for the establishment of the Prize. ;Matteucci Medalists * 1868 Hermann Helmholtz * 1875 Henri Victor Regnault * 1876 William Thomson, 1st Baron Kelvin * 1877 Gustav Kirchhoff * 1878 Gustav Wiedemann * 1879 Wilhelm Eduard Weber * 1880 Antonio Pacinotti * 1881 Emilio Villari * 1882 Augusto Righi * 1887 Thomas Edison * 1888 Heinrich Rudolph Hertz * 1894 John Strutt, 3rd Baron Rayleigh * 1895 Henry Augustus Rowland * 1896 Wilhelm Conrad Röntgen and Philipp Lenard * 1901 Guglielmo Marconi * 1903 Albert Abraham Michelson * 1904 Marie Curie and Pierre Curie * 1905 Henri Poincaré * 1906 James Dewar * 1907 William Ramsay ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gauss's Principle Of Least Constraint
The principle of least constraint is one variational formulation of classical mechanics enunciated by Carl Friedrich Gauss in 1829, equivalent to all other formulations of analytical mechanics. Intuitively, it says that the acceleration of a constrained physical system will be as similar as possible to that of the corresponding unconstrained system. Statement The principle of least constraint is a least squares principle stating that the true accelerations of a mechanical system of n masses is the minimum of the quantity : Z \, \stackrel \sum_^ m_j \cdot \left, \, \ddot \mathbf_j - \frac \^ where the ''j''th particle has mass m_j, position vector \mathbf_j, and applied non-constraint force \mathbf_j acting on the mass. The notation \dot \mathbf indicates time derivative of a vector function \mathbf(t), i.e. position. The corresponding accelerations \ddot \mathbf_j satisfy the imposed constraints, which in general depends on the current state of the system, \. It is reca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hertz–Knudsen Equation
In surface chemistry, the Hertz–Knudsen equation, also known as Knudsen-Langmuir equation describes evaporation rates, named after Heinrich Hertz and Martin Knudsen Martin Hans Christian Knudsen (February 15, 1871 in Hasmark on Funen – May 27, 1949 in Copenhagen) was a Danish physicist who taught and conducted research at the Technical University of Denmark. He is primarily known for his study of molec .... Applications Non-dissociative adsorption (Langmuirian adsorption) The Hertz–Knudsen equation describes the sticking of gas molecules on a surface by expressing the time rate of change of the concentration of molecules on the surface as a function of the pressure of the gas and other parameters:R. B. DarlingEE-527: Micro Fabrication Virginia University (retrieved Feb. 9 2015). :\frac\frac \equiv \varphi = \frac = \frac, where: See also * Langmuir (unit) References {{DEFAULTSORT:Hertz-Knudsen equation Surface science ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hertz Vector
Hertz vectors, or the Hertz vector potentials, are an alternative formulation of the electromagnetic potentials. They are most often introduced in electromagnetic theory textbooks as practice problems for students to solve.E.A. Essex"Hertz vector potentials of electromagnetic theory" ''American Journal of Physics'' 45, 1099 (1977); doi: 10.1119/1.10955 There are multiple cases where they have a practical use, including antennas and waveguides.H. R. L. Lamont, Wave Guides, (Metheun, London, 1963). Though they are sometimes used in such practice problems, they are still rarely mentioned in most electromagnetic theory courses, and when they are they are often not practiced in a manner that demonstrates when they may be useful or provide a simpler method to solving a problem than more commonly practiced methods. Overview Hertz vectors can be advantageous when solving for the electric and magnetic fields in certain scenarios, as they provide an alternative way to define the scalar po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
