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Physics

Work

In general, work is defined as a productive activity, which implies the implementation of rigorous and methodical, intellectual and/or manual knowledge, to produce and distribute goods and services in exchange for compensation, monetary or otherwise, an important topic of study for both social sciences (sociology, politics, law, economics) that the abstract and natural sciences (physics and geography). […]

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Bioluminescence

Bioluminescence is a type of reaction that involves the emission of electromagnetic radiation in the visible and near infrared, by certain living organisms. Bioluminescence is to be considered a particular case of another phenomenon, luminescence. The latter is characterized by the emission of radiation without the emission of heat. For luminescence to occur, there must be

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Electric displacement field

In physics, electric induction, also called electric displacement field, is a vector field used in electromagnetism to describe the electric polarization of a dielectric material following the application of an electric field. It is a generalization of the electric field used in Maxwell’s equations to describe the effect of polarization charges on the spatial and temporal configuration

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Laser

A laser optoelectronic device capable of emitting a coherent beam of light (a unidirectional, monochromatic radiation with a wavelength between infrared and ultraviolet) through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term “laser“ originated as an acronym for “light amplification by stimulated emission of radiation“. The first laser was built

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Gamma ray

In nuclear physics gamma rays, often indicated with the corresponding lower case Greek letter γ, are the electromagnetic radiations produced by radioactive decay of atomic nuclei. They are very high frequency radiations and they are among the most dangerous for man, as all ionizing radiations. The danger derives from the fact that they are high energy

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Candoluminescence

Candoluminescence is the (archaic) term used to describe the light given off by certain materials which have been heated to incandescence and emit light at shorter wavelengths than would be expected for a typical blackbody radiator. The phenomenon is noted in certain transition metal and rare earth metal oxide materials (ceramics) such as zinc oxide and cerium oxide or thorium dioxide, where some of the light from incandescence causes fluorescence of the material.

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Sublimation

Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state; this transformation occurs with heat acquisition and is, therefore, an endothermic process. Usually, in normal environmental conditions, to pass from solid to gaseous state it is necessary to go through the liquid state. Under certain pressure conditions, as the

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Airglow

Airglow or nocturnal luminescence is a weak light emission from the Earth’s atmosphere; as a result, the night sky is never completely dark. It was first noticed in 1868 by Anders Jonas Ångström and it is caused by a set of processes in the upper layers of the atmosphere, such as the recombination of ions that

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Refraction

In physics, refraction (from medieval Latin refractio-onis, from refractus, refracted) is the change in direction of a wave passing from one medium to another or from a gradual change in the medium with a different refractive index (\(n\)). In optics, the refractive index or index of refraction of a material is a dimensionless number that describes how fast light

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Weak interaction

The weak interaction, which is also often called the weak force or weak nuclear force, is responsible for some nuclear phenomena such as beta decay of the atomic nuclei associated with radioactivity and acts between leptons and quarks (semileptonic interactions), between only leptons (leptonic interactions) and between only quarks (non-leptonic interactions) through the exchange of massive vector bosons called

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Electrochemiluminescence

Electrochemiluminescence or electrogenerated chemiluminescence (ECL) is a kind of luminescence produced during electrochemical reactions in solutions. In electrochemiluminescence, electrochemically generated intermediates undergo a high degree of exergonic reaction to produce an electronically excited state and then emits light when relaxed to a lower energy level. This wavelength of emitted photons corresponds to the energy gap between these two states. ECL

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Luminous intensity

Luminous intensity is a physical quantity whose unit of measurement in the International System is the candela. The luminous intensity (I_{textrm{V}}) of a point source in a given direction in the unit solid angle is the luminous flux. It belongs, among other groupings of physical quantities, to the group of photometric quantities. In other words, the

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Kinematics

Kinematics (from the French term cinématique, coined by the physicist André-Marie Ampère from the greek κίνημα -ατος, kinema -atos = “movement”, derived in turn from the verb κινέω, kineo = “to move”) is that branch of Newtonian mechanics that deals with quantitatively describing the motion of bodies, using only the notions of space and time, regardless

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Luminous flux

In photometry, luminous flux (or luminous power) is a photometric quantity that measures the perceived power of light. The sensitivity of the human eye varies according to the wavelength of the light emitted. The luminous flux differs from the radiant flux, which is instead the measure of the total power of electromagnetic radiation emitted. The luminous flux

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Molecule-based magnets

Molecule-based magnets are materials with magnetic properties similar to those of common ferromagnets (e.g. iron, cobalt, nickel), but in which these properties originate from the electronic characteristics of the molecules that compose it. The difference from traditional magnets is that in the latter, the magnetic behavior is based on a collective property of atoms, with non-zero

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London dispersion force

London dispersion forces (LDF, also known as dispersion forces, London forces, instantaneous dipole–induced dipole forces, Fluctuating Induced Dipole Bonds or loosely as van der Waals forces) identify all those forces that occur at the atomic and molecular level due to instantaneous multipoles as a result of quantum effects. These forces are part of the broader category of van der Waals forces.

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Ferrimagnetism

Ferrimagnetism is a type of permanent magnetism that occurs in some crystals when the magnetic moments of nearby ions tend to align antiparallel: it is, therefore, a type of antiferromagnetism; this situation occurs mainly in compounds known as ferrites. The term ferrimagnetism was originally proposed by Néel to describe the magnetic ordering phenomena in ferrites, in which iron

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Gravitational field

In physics, the gravitational field is the field associated with gravitational interaction. A gravitational field is a model used to explain the influence that a massive body extends into the space around itself, producing a force on another massive body. Each body with mass exerts on other bodies an attractive force, which is called “gravitational attraction”. It is proportional

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Resonance

Resonance is the phenomenon by which an oscillating system is able to absorb energy from an external source in a particularly efficient way only at one (or more) very precise frequencies. Let’s examine the characteristics: Examples of resonance phenomena Natural phenomena The phenomenon of resonance characterizes all systems that have the two properties necessary to allow

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X-ray

X-rays are also called Röntgen rays, from the name of the German physicist Konrad Wilhelm Röntgen who discovered them in 1895, demonstrating their existence through an X-ray of his wife’s hand. X-rays make up X-radiation, a form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 0.1 to 10 nanometers, corresponding to frequencies in the range 30 petahertz

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Rheology

Rheology (/riːˈɒlədʒi/; from Greek ῥέω rhéō, ‘flow’ and -λoγία, -logia, ‘study of’) is the science that studies the equilibrium reached in deformed matter due to stresses (as a result of the action of a force and in relation to: the intensity of the force; the duration of application of the force; the speed of application of the force), primarily in a

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Dehumidification

Dehumidification is the process of removing humidity from a system. The dehumidification of aeriformes can be done purely physically or physicochemically. The dehumidification by physical means is obtained by subjecting the aeriform to cooling until it reaches saturation, after which further cooling causes the condensation of water and other vapors that may be present. A subsequent

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Diffraction

Diffraction refers to various phenomena that occur when a wave encounters an obstacle or a slit. In general, diffraction is defined as the spreading or bending of waves as they pass round the edge of an obstacle or through an opening whose size is roughly the same as the wavelength of the waves. The disturbed waves

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Gravity

Gravity, or gravitation, is a natural phenomenon that manifests itself with a force by which all things with mass or energy—including planets, stars, galaxies, and even light—are brought toward (or gravitate toward) one another. Gravity is the first force to be postulated as an action-at-a-distance force, that is, objects exert a gravitational force on one another without physical contact

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