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Black Body Spectrum
BLACK-BODY RADIATION is the thermal electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, or emitted by a black body (an opaque and non-reflective body). It has a specific spectrum and intensity that depends only on the body's temperature, which is assumed for the sake of calculations and theory to be uniform and constant. The thermal radiation spontaneously emitted by many ordinary objects can be approximated as black-body radiation. A perfectly insulated enclosure that is in thermal equilibrium internally contains black-body radiation and will emit it through a hole made in its wall, provided the hole is small enough to have negligible effect upon the equilibrium
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Draper Point
The DRAPER POINT is the approximate temperature above which almost all solid materials visibly glow as a result of blackbody radiation . It was established at 977 °F (525 °C, 798 K) by John William Draper in 1847. Bodies at temperatures just below the Draper point radiate primarily in the infrared range and emit negligible visible light. The value of the Draper point can be calculated using Wien\'s displacement law : the peak frequency peak {displaystyle nu _{text{peak}}} (in hertz ) emitted by a blackbody relates to temperature as follows: peak = 2.821 k T h , {displaystyle nu _{text{peak}}=2.821{frac {kT}{h}},} where k is Boltzmann\'s constant , h is Planck\'s constant , T is temperature (in kelvins ). Substituting the Draper point into this equation produces a frequency of 83 THz, or a wavelength of 3.6 µm , which is well into the infrared and completely invisible to the human eye
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Carbon Black
CARBON BLACK (subtypes are ACETYLENE BLACK, CHANNEL BLACK, FURNACE BLACK, LAMP BLACK and THERMAL BLACK) is a material produced by the incomplete combustion of heavy petroleum products such as FCC tar, coal tar , ethylene cracking tar, and a small amount from vegetable oil . Carbon black
Carbon black
is a form of paracrystalline carbon that has a high surface-area-to-volume ratio , albeit lower than that of activated carbon . It is dissimilar to soot in its much higher surface-area-to-volume ratio and significantly lower (negligible and non-bioavailable) PAH (polycyclic aromatic hydrocarbon) content. However, carbon black is widely used as a model compound for diesel soot for diesel oxidation experiments. Carbon black
Carbon black
is mainly used as a reinforcing filler in tires and other rubber products. In plastics, paints, and inks carbon black is used as a color pigment
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Radiative Equilibrium
RADIATIVE EQUILIBRIUM is one of the several requirements for thermodynamic equilibrium , but it can occur in the absence of thermodynamic equilibrium. There are various types of radiative equilibrium, which is itself a kind of dynamic equilibrium . CONTENTS* 1 Definitions * 1.1 Prevost\'s definitions * 1.2 Pointwise radiative equilibrium * 1.2.1 Approximate pointwise radiative equilibrium * 1.3 Radiative exchange equilibrium * 1.3.1 Approximate radiative exchange equilibrium * 1.4 Definition for an entire passive celestial system such as a planet that does not supply its own energy * 1.4.1 Global radiative equilibrium * 1.5 Definition for an entire active celestial system such as a star that supplies its own energy * 1.5.1 A contrary definition * 2 Mechanisms of radiative equilibrium * 3 References DEFINITIONSThere are several types of radiative equilibrium
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Detailed Balance
The principle of DETAILED BALANCE is formulated for kinetic systems which are decomposed into elementary processes (collisions, or steps, or elementary reactions): At equilibrium , each elementary process should be equilibrated by its reverse process. CONTENTS * 1 History * 2 Microscopic background * 3 Reversible Markov chains * 4 Detailed balance and entropy increase * 5 Wegscheider\'s conditions for the generalized mass action law * 6 Dissipation in systems with detailed balance * 7 Onsager reciprocal relations and detailed balance * 8 Semi-detailed balance * 9 Dissipation in systems with semi-detailed balance * 10 Detailed balance for systems with irreversible reactions * 11 See also * 12 References HISTORYThe principle of detailed balance was explicitly introduced for collisions by Ludwig Boltzmann
Ludwig Boltzmann
. In 1872, he proved his H-theorem using this principle
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Kirchhoff's Law Of Thermal Radiation
In heat transfer , KIRCHHOFF\'S LAW OF THERMAL RADIATION refers to wavelength-specific radiative emission and absorption by a material body in thermodynamic equilibrium , including radiative exchange equilibrium. A body at temperature T radiates electromagnetic energy . A perfect black body in thermodynamic equilibrium absorbs all light that strikes it, and radiates energy according to a unique law of radiative emissive power for temperature T, universal for all perfect black bodies. Kirchhoff's law states that: For a body of any arbitrary material emitting and absorbing thermal electromagnetic radiation at every wavelength in thermodynamic equilibrium, the ratio of its emissive power to its dimensionless coefficient of absorption is equal to a universal function only of radiative wavelength and temperature. That universal function describes the perfect black-body emissive power
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Graphite
GRAPHITE ( /ˈɡræfaɪt/ ), archaically referred to as PLUMBAGO, is a crystalline allotrope of carbon , a semimetal and a native element mineral . Graphite
Graphite
is the most stable form of carbon under standard conditions . Therefore, it is used in thermochemistry as the standard state for defining the heat of formation of carbon compounds
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Wavelength
In physics , the WAVELENGTH of a sinusoidal wave is the SPATIAL PERIOD of the wave—the distance over which the wave's shape repeats, and thus the inverse of the spatial frequency . It is usually determined by considering the distance between consecutive corresponding points of the same phase , such as crests, troughs, or zero crossings and is a characteristic of both traveling waves and standing waves , as well as other spatial wave patterns. Wavelength is commonly designated by the Greek letter
Greek letter
lambda (λ). The concept can also be applied to periodic waves of non-sinusoidal shape. The term wavelength is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids
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Baryon
A BARYON is a composite subatomic particle made up of three quarks (a TRIQUARK, as distinct from mesons , which are composed of one quark and one antiquark ). Baryons and mesons belong to the hadron family of particles , which are the quark-based particles. The name "baryon" comes from the Greek word for "heavy" (βαρύς, barys), because, at the time of their naming, most known elementary particles had lower masses than the baryons. As quark-based particles, baryons participate in the strong interaction , whereas leptons , which are not quark-based, do not. The most familiar baryons are the protons and neutrons that make up most of the mass of the visible matter in the universe . Electrons (the other major component of the atom ) are leptons. Each baryon has a corresponding antiparticle (antibaryon) where quarks are replaced by their corresponding antiquarks
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Absolute Zero
ABSOLUTE ZERO is the lower limit of the thermodynamic temperature scale, a state at which the enthalpy and entropy of a cooled ideal gas reaches its minimum value, taken as 0. The theoretical temperature is determined by extrapolating the ideal gas law ; by international agreement, absolute zero is taken as −273.15° on the Celsius scale ( International System of Units ), which equates to −459.67° on the Fahrenheit scale ( United States customary units or Imperial units ). The corresponding Kelvin and Rankine temperature scales set their zero points at absolute zero by definition
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Spontaneous Process
A SPONTANEOUS PROCESS is the time-evolution of a system in which it releases free energy and moves to a lower, more thermodynamically stable energy state. The sign convention of changes in free energy follows the general convention for thermodynamic measurements, in which a release of free energy from the system corresponds to a negative change in free energy, but a positive change for the surroundings. Depending on the nature of the process, the free energy is determined differently. For example, the Gibbs free energy
Gibbs free energy
is used when considering processes that occur under constant pressure and temperature conditions whereas the Helmholtz free energy
Helmholtz free energy
is used when considering processes that occur under constant volume and temperature conditions. Because spontaneous processes are characterized by a decrease in the system's free energy, they do not need to be driven by an outside source of energy
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Entropy
In statistical mechanics , ENTROPY (usual symbol S) is related to the number of microscopic configurations Ω that a thermodynamic system can have when in a state as specified by some macroscopic variables. Specifically, assuming for simplicity that each of the microscopic configurations is equally probable, the entropy of the system is the natural logarithm of that number of configurations, multiplied by the Boltzmann constant kB. Formally, S = k B ln (assuming equiprobable states) . {displaystyle S=k_{mathrm {B} }ln Omega ~~{mbox{(assuming equiprobable states)}}.} This is consistent with 19th century formulas for entropy in terms of heat and temperature, as discussed below. Boltzmann's constant, and therefore entropy, have dimensions of energy divided by temperature . For example, gas in a container with known volume, pressure, and energy could have an enormous number of possible configurations of the collection of individual gas molecules
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Temperature
A TEMPERATURE is an objective comparative measurement of hot or cold. It is measured by a thermometer . Several scales and units exist for measuring temperature, the most common being the Celsius scale (with units denoted °C; formerly called degrees centigrade), the Fahrenheit scale (with units denoted °F), and, especially in science, the Kelvin scale (with units denoted K). The coldest theoretical temperature is absolute zero , at which the thermal motion of atoms and molecules reaches its minimum – classically, this would be a state of motionlessness, but quantum uncertainty dictates that the particles still possess a finite zero-point energy . Absolute zero
Absolute zero
is denoted as 0 K on the Kelvin scale, −273.15 °C on the Celsius scale, and −459.67 °F on the Fahrenheit
Fahrenheit
scale
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Hohlraum
In radiation thermodynamics , a HOHLRAUM (a non-specific German word for a "hollow area" or "cavity") is a cavity whose walls are in radiative equilibrium with the radiant energy within the cavity. This idealized cavity can be approximated in practice by making a small perforation in the wall of a hollow container of any opaque material. The radiation escaping through such a perforation will be a good approximation to black-body radiation at the temperature of the interior of the container. CONTENTS * 1 Inertial confinement fusion
Inertial confinement fusion
* 2 Nuclear weapon design * 3 Notes and references * 4 External links INERTIAL CONFINEMENT FUSION Mockup of a gold-plated hohlraum designed for use in the National Ignition Facility The indirect drive approach to inertial confinement fusion is as follows; the fusion fuel capsule is held inside a cylindrical hohlraum
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Electromagnetism
ELECTROMAGNETISM is a branch of physics involving the study of the ELECTROMAGNETIC FORCE, a type of physical interaction that occurs between electrically charged particles. The electromagnetic force usually exhibits electromagnetic fields such as electric fields , magnetic fields , and light and is one of the four fundamental interactions (commonly called forces) in nature . The other three fundamental interactions are the strong interaction , the weak interaction and gravitation . Lightning
Lightning
is an electrostatic discharge that travels between two charged regions. The word electromagnetism is a compound form of two Greek terms, ἤλεκτρον ēlektron, "amber ", and μαγνῆτις λίθος magnētis lithos, which means "Μagnesian stone", a type of iron ore
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Thermodynamics
THERMODYNAMICS is a branch of physics concerned with heat and temperature and their relation to energy and work . The behavior of these quantities is governed by the four laws of thermodynamics , irrespective of the composition or specific properties of the material or system in question. The laws of thermodynamics are explained in terms of microscopic constituents by statistical mechanics . Thermodynamics
Thermodynamics
applies to a wide variety of topics in science and engineering , especially physical chemistry , chemical engineering and mechanical engineering . Historically, thermodynamics developed out of a desire to increase the efficiency of early steam engines , particularly through the work of French physicist Nicolas Léonard Sadi Carnot (1824) who believed that engine efficiency was the key that could help France win the Napoleonic Wars
Napoleonic Wars

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