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110-652: [REDACTED] Look up 電 , 稲妻 , or いなずま in Wiktionary, the free dictionary. Inazuma ( 電 / 稲妻 / いなずま / いなづま , " lightning ") : may refer to: Suzuki Inazuma 250 , a motorcycle Japanese destroyer  Inazuma , four destroyers of the Imperial Japanese Navy and the Japan Maritime Self-Defense Force Lightning (1952 film) , or Inazuma ,

220-466: A b s = P e m t b b {\displaystyle P_{\rm {abs}}=P_{\rm {emt\,bb}}} , is known as the effective temperature . The actual temperature of the planet will likely be different, depending on its surface and atmospheric properties. Ignoring the atmosphere and greenhouse effect, the planet, since it is at a much lower temperature than the Sun, emits mostly in

330-508: A thundercloud moves over the surface of the Earth, an equal electric charge , but of opposite polarity, is induced on the Earth's surface underneath the cloud. The induced positive surface charge, when measured against a fixed point, will be small as the thundercloud approaches, increasing as the center of the storm arrives and dropping as the thundercloud passes. The referential value of the induced surface charge could be roughly represented as

440-506: A "ghostly" grey (the visible light is actually red, but low intensity light activates only the eye's grey-level sensors). With rising temperature, the glow becomes visible even when there is some background surrounding light: first as a dull red, then yellow, and eventually a "dazzling bluish-white" as the temperature rises. When the body appears white, it is emitting a substantial fraction of its energy as ultraviolet radiation . The Sun , with an effective temperature of approximately 5800 K,

550-474: A 40-year-old male is about 35 kcal/(m ·h), which is equivalent to 1700 kcal per day, assuming the same 2 m area. However, the mean metabolic rate of sedentary adults is about 50% to 70% greater than their basal rate. There are other important thermal loss mechanisms, including convection and evaporation . Conduction is negligible – the Nusselt number is much greater than unity. Evaporation by perspiration

660-572: A Japanese film by Mikio Naruse Inazuma, an Usagi Yojimbo character Inazuma Eleven , an association-football-themed media franchise Inazuma, Teyvat  [ zh ] , a region in Genshin Impact People with the surname [ edit ] Inazuma Raigorō (1802–1877), Japanese sumo wrestler See also [ edit ] Azuma (disambiguation) Ikazuchi (disambiguation) Lightning (disambiguation) Raiden (disambiguation) Topics referred to by

770-461: A base and carbon dioxide is an acidic gas, it is possible that charged water clouds in which the negative charge is in the form of the aqueous hydroxide ion, interact with atmospheric carbon dioxide to form aqueous carbonate ions and aqueous hydrogen carbonate ions. The typical cloud-to-ground lightning flash culminates in the formation of an electrically conducting plasma channel through the air in excess of 5 km (3.1 mi) tall, from within

880-523: A bell curve. The oppositely charged regions create an electric field within the air between them. This electric field varies in relation to the strength of the surface charge on the base of the thundercloud – the greater the accumulated charge, the higher the electrical field. The best-studied and understood form of lightning is cloud to ground (CG) lightning. Although more common, intra-cloud (IC) and cloud-to-cloud (CC) flashes are very difficult to study given there are no "physical" points to monitor inside

990-459: A bidirectional leader initiates between the main negative and lower positive charge regions in a thundercloud. The weaker positive charge region is filled quickly by the negative leader which then propagates toward the inductively-charged ground. The positively and negatively charged leaders proceed in opposite directions, positive upwards within the cloud and negative towards the earth. Both ionic channels proceed, in their respective directions, in

1100-403: A black body at room temperature ( 300 K ) with one square meter of surface area will emit a photon in the visible range (390–750 nm) at an average rate of one photon every 41 seconds, meaning that, for most practical purposes, such a black body does not emit in the visible range. The study of the laws of black bodies and the failure of classical physics to describe them helped establish

1210-421: A black body surface, the spectral radiance density (defined per unit of area normal to the propagation) is independent of the angle θ {\displaystyle \theta } of emission with respect to the normal. However, this means that, following Lambert's cosine law , B ν ( T ) cos ⁡ θ {\displaystyle B_{\nu }(T)\cos \theta }

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1320-545: A brilliant, blue-white color. Once the electric current stops flowing, the channel cools and dissipates over tens or hundreds of milliseconds, often disappearing as fragmented patches of glowing gas. The nearly instantaneous heating during the return stroke causes the air to expand explosively, producing a powerful shock wave which is heard as thunder . High-speed videos (examined frame-by-frame) show that most negative CG lightning flashes are made up of 3 or 4 individual strokes, though there may be as many as 30. Each re-strike

1430-405: A cavity. In equilibrium, for each frequency, the intensity of radiation which is emitted and reflected from a body relative to other frequencies (that is, the net amount of radiation leaving its surface, called the spectral radiance ) is determined solely by the equilibrium temperature and does not depend upon the shape, material or structure of the body. For a black body (a perfect absorber) there

1540-400: A characteristic frequency distribution that depends on the temperature. Its emission is called blackbody radiation. The concept of the black body is an idealization, as perfect black bodies do not exist in nature. However, graphite and lamp black , with emissivities greater than 0.95, are good approximations to a black material. Experimentally, blackbody radiation may be established best as

1650-421: A charge opposite of that of the leader tip. The negative end of the bidirectional leader fills a positive charge region, also called a well, inside the cloud while the positive end fills a negative charge well. Leaders often split, forming branches in a tree-like pattern. In addition, negative and some positive leaders travel in a discontinuous fashion, in a process called "stepping". The resulting jerky movement of

1760-405: A condition of thermodynamic equilibrium. In the laboratory, blackbody radiation is approximated by the radiation from a small hole in a large cavity, a hohlraum , in an entirely opaque body that is only partly reflective, that is maintained at a constant temperature. (This technique leads to the alternative term cavity radiation .) Any light entering the hole would have to reflect off the walls of

1870-410: A conductive portion of the main leader network, a return stroke-like process occurs and a dart leader travels across all or a portion of the length of the original leader. The dart leaders making connections with the ground are what cause a majority of subsequent return strokes. Each successive stroke is preceded by intermediate dart leader strokes that have a faster rise time but lower amplitude than

1980-428: A conversion of a body's internal energy into electromagnetic energy, and is therefore called thermal radiation . It is a spontaneous process of radiative distribution of entropy . Conversely, all normal matter absorbs electromagnetic radiation to some degree. An object that absorbs all radiation falling on it, at all wavelengths , is called a black body. When a black body is at a uniform temperature, its emission has

2090-668: A crude estimate. Ambient air motion, causing forced convection, or evaporation reduces the relative importance of radiation as a thermal-loss mechanism. Application of Wien's law to human-body emission results in a peak wavelength of λ peak = 2.898 × 10 − 3   K ⋅ m 305   K = 9.50   μ m . {\displaystyle \lambda _{\text{peak}}=\mathrm {\frac {2.898\times 10^{-3}~K\cdot m}{305~K}} =\mathrm {9.50~\mu m} .} For this reason, thermal imaging devices for human subjects are most sensitive in

2200-452: A function of the cavity temperature alone. A graph of the spectral radiation intensity plotted versus frequency(or wavelength) is called the blackbody curve . Different curves are obtained by varying the temperature. When the body is black, the absorption is obvious: the amount of light absorbed is all the light that hits the surface. For a black body much bigger than the wavelength, the light energy absorbed at any wavelength λ per unit time

2310-482: A great distance but not heard; dry lightning , which can cause forest fires ; and ball lightning , which is rarely observed scientifically. Humans have deified lightning for millennia. Idiomatic expressions derived from lightning, such as the English expression "bolt from the blue", are common across languages. At all times people have been fascinated by the sight and difference of lightning. The fear of lightning

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2420-446: A high-resistance medium must obstruct the free, unimpeded equalization of the opposite charges. The atmosphere provides the electrical insulation, or barrier, that prevents free equalization between charged regions of opposite polarity. It is well understood that during a thunderstorm there is charge separation and aggregation in certain regions of the cloud; however, the exact processes by which this occurs are not fully understood. As

2530-692: A local maximum or peak, λ peak {\displaystyle \lambda _{\text{peak}}} , is a function only of the temperature: λ peak = b T , {\displaystyle \lambda _{\text{peak}}={\frac {b}{T}},} where the constant b , known as Wien's displacement constant, is equal to h c k 1 5 + W 0 ( − 5 e − 5 ) ≈ {\displaystyle {\frac {hc}{k}}{\frac {1}{5+W_{0}(-5e^{-5})}}\approx } 2.897 771 955 × 10  m K . W 0 {\displaystyle W_{0}}

2640-420: A mathematical expression fitting the experimental data satisfactorily. Planck had to assume that the energy of the oscillators in the cavity was quantized, which is to say that it existed in integer multiples of some quantity. Einstein built on this idea and proposed the quantization of electromagnetic radiation itself in 1905 to explain the photoelectric effect . These theoretical advances eventually resulted in

2750-412: A negative charge. Updrafts within a storm cloud separate the lighter ice crystals from the heavier graupel, causing the top region of the cloud to accumulate a positive space charge while the lower level accumulates a negative space charge. Because the concentrated charge within the cloud must exceed the insulating properties of air, and this increases proportionally to the distance between the cloud and

2860-453: A nonphysical spectrum of emitted radiation that grows without bound with increasing frequency, a problem known as the ultraviolet catastrophe . In the longer wavelengths this deviation is not so noticeable, as h ν {\displaystyle h\nu } and n h ν {\displaystyle nh\nu } are very small. In the shorter wavelengths of the ultraviolet range, however, classical theory predicts

2970-601: A number of much shorter flashes (strokes) of around 60 to 70 microseconds . Many factors affect the frequency, distribution, strength and physical properties of a typical lightning flash in a particular region of the world. These factors include ground elevation, latitude , prevailing wind currents, relative humidity , and proximity to warm and cold bodies of water. To a certain degree, the proportions of intra-cloud, cloud-to-cloud, and cloud-to-ground lightning may also vary by season in middle latitudes . Because human beings are terrestrial and most of their possessions are on

3080-466: A number of successive spurts. Each leader "pools" ions at the leading tips, shooting out one or more new leaders, momentarily pooling again to concentrate charged ions, then shooting out another leader. The negative leader continues to propagate and split as it heads downward, often speeding up as it gets closer to the Earth's surface. About 90% of ionic channel lengths between "pools" are approximately 45 m (148 ft) in length. The establishment of

3190-451: A threshold and form upward streamers. Once a downward leader connects to an available upward leader, a process referred to as attachment, a low-resistance path is formed and discharge may occur. Photographs have been taken in which unattached streamers are clearly visible. The unattached downward leaders are also visible in branched lightning, none of which are connected to the earth, although it may appear they are. High-speed videos can show

3300-549: A unit of area per unit time, T is the absolute temperature, and σ = 5.670 367 × 10  W·m ⋅K is the Stefan–Boltzmann constant . Planck's law states that B ν ( T ) = 2 h ν 3 c 2 1 e h ν / k T − 1 , {\displaystyle B_{\nu }(T)={\frac {2h\nu ^{3}}{c^{2}}}{\frac {1}{e^{h\nu /kT}-1}},} where For

3410-487: Is an atmospheric electrical phenomenon and contributes to the global atmospheric electrical circuit . The three main kinds of lightning are distinguished by where they occur: either inside a single thundercloud (intra-cloud), between two clouds (cloud-to-cloud), or between a cloud and the ground (cloud-to-ground), in which case it is referred to as a lightning strike . Many other observational variants are recognized, including " heat lightning ", which can be seen from

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3520-419: Is an approximate black body with an emission spectrum peaked in the central, yellow-green part of the visible spectrum , but with significant power in the ultraviolet as well. Blackbody radiation provides insight into the thermodynamic equilibrium state of cavity radiation. All normal ( baryonic ) matter emits electromagnetic radiation when it has a temperature above absolute zero . The radiation represents

3630-568: Is called astraphobia . The first known photograph of lightning is from 1847, by Thomas Martin Easterly . The first surviving photograph is from 1882, by William Nicholson Jennings ,  a photographer who spent half his life capturing pictures of lightning and proving its diversity. There is growing evidence that lightning activity is increased by particulate emissions (a form of air pollution). However, lightning may also improve air quality and clean greenhouse gases such as methane from

3740-492: Is different from Wikidata All article disambiguation pages All disambiguation pages Lightning Lightning is a natural phenomenon formed by electrostatic discharges through the atmosphere between two electrically charged regions, either both in the atmosphere or one in the atmosphere and one on the ground , temporarily neutralizing these in a near-instantaneous release of an average of between 200 megajoules and 7 gigajoules of energy , depending on

3850-412: Is no reflected radiation, and so the spectral radiance is entirely due to emission. In addition, a black body is a diffuse emitter (its emission is independent of direction). Blackbody radiation becomes a visible glow of light if the temperature of the object is high enough. The Draper point is the temperature at which all solids glow a dim red, about 798 K . At 1000 K , a small opening in

3960-408: Is only required if radiation and convection are insufficient to maintain a steady-state temperature (but evaporation from the lungs occurs regardless). Free-convection rates are comparable, albeit somewhat lower, than radiative rates. Thus, radiation accounts for about two-thirds of thermal energy loss in cool, still air. Given the approximate nature of many of the assumptions, this can only be taken as

4070-413: Is peaked at a characteristic frequency that shifts to higher frequencies with increasing temperature, and at room temperature most of the emission is in the infrared region of the electromagnetic spectrum . As the temperature increases past about 500 degrees Celsius , black bodies start to emit significant amounts of visible light. Viewed in the dark by the human eye, the first faint glow appears as

4180-420: Is related to the photon flux density b ν ( T , E ) {\displaystyle b_{\nu }(T,E)} through B ν ( T , E ) = E b ν ( T , E ) {\displaystyle B_{\nu }(T,E)=Eb_{\nu }(T,E)} Wien's displacement law shows how the spectrum of blackbody radiation at any temperature

4290-400: Is related to the spectrum at any other temperature. If we know the shape of the spectrum at one temperature, we can calculate the shape at any other temperature. Spectral intensity can be expressed as a function of wavelength or of frequency. A consequence of Wien's displacement law is that the wavelength at which the intensity per unit wavelength of the radiation produced by a black body has

4400-418: Is separated by a relatively large amount of time, typically 40 to 50 milliseconds, as other charged regions in the cloud are discharged in subsequent strokes. Re-strikes often cause a noticeable " strobe light " effect. To understand why multiple return strokes utilize the same lightning channel, one needs to understand the behavior of positive leaders, which a typical ground flash effectively becomes following

4510-403: Is strictly proportional to the blackbody curve. This means that the blackbody curve is the amount of light energy emitted by a black body, which justifies the name. This is the condition for the applicability of Kirchhoff's law of thermal radiation : the blackbody curve is characteristic of thermal light, which depends only on the temperature of the walls of the cavity, provided that the walls of

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4620-477: Is strongest on grounded objects whose tops are closest to the base of the thundercloud, such as trees and tall buildings. If the electric field is strong enough, a positively charged ionic channel, called a positive or upward streamer , can develop from these points. This was first theorized by Heinz Kasemir. As negatively charged leaders approach, increasing the localized electric field strength, grounded objects already experiencing corona discharge will exceed

4730-728: Is the Lambert W function . So λ peak {\displaystyle \lambda _{\text{peak}}} is approximately 2898 μm/T, with the temperature given in kelvins. At a typical room temperature of 293 K (20 °C), the maximum intensity is at 9.9 μm . Planck's law was also stated above as a function of frequency. The intensity maximum for this is given by ν peak = T × 5.879... × 10 10   H z / K . {\displaystyle \nu _{\text{peak}}=T\times 5.879...\times 10^{10}\ \mathrm {Hz} /\mathrm {K} .} In unitless form,

4840-514: Is the albedo or reflectance of the planet in the UV-Vis range. In other words, the planet absorbs a fraction 1 − α {\displaystyle 1-\alpha } of the Sun's light, and reflects the rest. The power absorbed by the planet and its atmosphere is then: Even though the planet only absorbs as a circular area π R 2 {\displaystyle \pi R^{2}} , it emits in all directions;

4950-598: Is the difference between the power emitted and the power absorbed: P net = P emit − P absorb . {\displaystyle P_{\text{net}}=P_{\text{emit}}-P_{\text{absorb}}.} Applying the Stefan–Boltzmann law, P net = A σ ε ( T 4 − T 0 4 ) , {\displaystyle P_{\text{net}}=A\sigma \varepsilon \left(T^{4}-T_{0}^{4}\right),} where A and T are

5060-443: Is the hypothetical blackbody radiation emitted by black holes , at a temperature that depends on the mass, charge, and spin of the hole. If this prediction is correct, black holes will very gradually shrink and evaporate over time as they lose mass by the emission of photons and other particles. A black body radiates energy at all frequencies, but its intensity rapidly tends to zero at high frequencies (short wavelengths). For example,

5170-561: Is the radiance density per unit area of emitting surface as the surface area involved in generating the radiance is increased by a factor 1 / cos ⁡ θ {\displaystyle 1/\cos \theta } with respect to an area normal to the propagation direction. At oblique angles, the solid angle spans involved do get smaller, resulting in lower aggregate intensities. The emitted energy flux density or irradiance B ν ( T , E ) {\displaystyle B_{\nu }(T,E)} ,

5280-460: Is usually negatively charged, this is where most CG lightning originates. This region is typically at the elevation where freezing occurs within the cloud. Freezing, combined with collisions between ice and water, appears to be a critical part of the initial charge development and separation process. During wind-driven collisions, ice crystals tend to develop a positive charge, while a heavier, slushy mixture of ice and water (called graupel ) develops

5390-458: The Kelvin water dropper . The most likely charge-carrying species were considered to be the aqueous hydrogen ion and the aqueous hydroxide ion. The electrical charging of solid water ice has also been considered. The charged species were again considered to be the hydrogen ion and the hydroxide ion. An electron is not stable in liquid water concerning a hydroxide ion plus dissolved hydrogen for

5500-470: The Stefan–Boltzmann constant . On a side note, at a distance d, the intensity d I {\displaystyle dI} per area d A {\displaystyle dA} of radiating surface is the useful expression d I = σ T 4 cos ⁡ θ π d 2 d A {\displaystyle dI=\sigma T^{4}{\frac {\cos \theta }{\pi d^{2}}}dA} when

5610-841: The Stefan–Boltzmann law : the power j * emitted per unit area of the surface of a black body is directly proportional to the fourth power of its absolute temperature: j ⋆ = σ T 4 , {\displaystyle j^{\star }=\sigma T^{4},} We used ∫ cos ⁡ θ d Ω = ∫ 0 2 π ∫ 0 π / 2 cos ⁡ θ sin ⁡ θ d θ d ϕ = π . {\displaystyle \int \cos \theta \,d\Omega =\int _{0}^{2\pi }\int _{0}^{\pi /2}\cos \theta \sin \theta \,d\theta \,d\phi =\pi .} The human body radiates energy as infrared light. The net power radiated

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5720-476: The triboelectric effect leading to electron or ion transfer between colliding bodies. Uncharged, colliding water-drops can become charged because of charge transfer between them (as aqueous ions) in an electric field as would exist in a thunder cloud. The main charging area in a thunderstorm occurs in the central part of the storm where air is moving upward rapidly (updraft) and temperatures range from −15 to −25 °C (5 to −13 °F); see Figure 1. In that area,

5830-584: The tropics where atmospheric convection is the greatest. This occurs from both the mixture of warmer and colder air masses , as well as differences in moisture concentrations, and it generally happens at the boundaries between them . The flow of warm ocean currents past drier land masses, such as the Gulf Stream , partially explains the elevated frequency of lightning in the Southeast United States . Because large bodies of water lack

5940-417: The 1840s as has the electrification of pure liquid water by the triboelectric effect. William Thomson (Lord Kelvin) demonstrated that charge separation in water occurs in the usual electric fields at the Earth's surface and developed a continuous electric field measuring device using that knowledge. The physical separation of charge into different regions using liquid water was demonstrated by Kelvin with

6050-423: The 7–14 micrometer range. The blackbody law may be used to estimate the temperature of a planet orbiting the Sun. The temperature of a planet depends on several factors: The analysis only considers the Sun's heat for a planet in a Solar System. The Stefan–Boltzmann law gives the total power (energy/second) that the Sun emits: where The Sun emits that power equally in all directions. Because of this,

6160-607: The Congo , where the elevation is around 975 m (3,200 ft). On average, this region receives 158 lightning strikes per square kilometre per year (410/sq mi/yr). Other lightning hotspots include Singapore and Lightning Alley in Central Florida . According to the World Meteorological Organization , on April 29, 2020, a bolt 768 km (477.2 mi) long was observed in

6270-424: The Earth where lightning can damage or destroy them, cloud-to-ground (CG) lightning is the most studied and best understood of the three types, even though in-cloud (IC) and cloud-to-cloud (CC) are more common types of lightning. Lightning's relative unpredictability limits a complete explanation of how or why it occurs, even after hundreds of years of scientific investigation. About 70% of lightning occurs over land in

6380-437: The atmosphere, while creating nitrogen oxide and ozone at the same time. Lightning is also the major cause of wildfire, and wildfire can contribute to climate change as well. More studies are warranted to clarify their relationship. The details of the charging process are still being studied by scientists, but there is general agreement on some of the basic concepts of thunderstorm electrification. Electrification can be by

6490-402: The attachment process in progress. Once a conductive channel bridges the air gap between the negative charge excess in the cloud and the positive surface charge excess below, there is a large drop in resistance across the lightning channel. Electrons accelerate rapidly as a result in a zone beginning at the point of attachment, which expands across the entire leader network at up to one third of

6600-412: The body surface area and temperature, ε {\displaystyle \varepsilon } is the emissivity , and T 0 is the ambient temperature. The total surface area of an adult is about 2 m , and the mid- and far-infrared emissivity of skin and most clothing is near unity, as it is for most nonmetallic surfaces. Skin temperature is about 33 °C, but clothing reduces

6710-432: The case of biased percolation, describes random connectivity phenomena, which produce an evolution of connected structures similar to that of lightning strikes. A streamer avalanche model has recently been favored by observational data taken by LOFAR during storms. When a stepped leader approaches the ground, the presence of opposite charges on the ground enhances the strength of the electric field . The electric field

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6820-399: The cavity are completely opaque and are not very reflective, and that the cavity is in thermodynamic equilibrium . When the black body is small, so that its size is comparable to the wavelength of light, the absorption is modified, because a small object is not an efficient absorber of light of long wavelength, but the principle of strict equality of emission and absorption is always upheld in

6930-401: The cavity multiple times before it escaped, in which process it is nearly certain to be absorbed. Absorption occurs regardless of the wavelength of the radiation entering (as long as it is small compared to the hole). The hole, then, is a close approximation of a theoretical black body and, if the cavity is heated, the spectrum of the hole's radiation (that is, the amount of light emitted from

7040-519: The cloud to the ground's surface. The actual discharge is the final stage of a very complex process. At its peak, a typical thunderstorm produces three or more strikes to the Earth per minute. Lightning primarily occurs when warm air is mixed with colder air masses, resulting in atmospheric disturbances necessary for polarizing the atmosphere. Lightning can also occur during dust storms , forest fires , tornadoes , volcanic eruptions , and even in

7150-476: The clouds. Also, given the very low probability of lightning striking the same point repeatedly and consistently, scientific inquiry is difficult even in areas of high CG frequency. In a process not well understood, a bidirectional channel of ionized air, called a " leader ", is initiated between oppositely-charged regions in a thundercloud. Leaders are electrically conductive channels of ionized gas that propagate through, or are otherwise attracted to, regions with

7260-424: The cold of winter, where the lightning is known as thundersnow . Hurricanes typically generate some lightning, mainly in the rainbands as much as 160 km (99 mi) from the center. Lightning is not distributed evenly around Earth . On Earth, the lightning frequency is approximately 44 (± 5) times per second, or nearly 1.4 billion flashes per year and the median duration is 0.52 seconds made up from

7370-431: The combination of temperature and rapid upward air movement produces a mixture of super-cooled cloud droplets (small water droplets below freezing), small ice crystals, and graupel (soft hail). The updraft carries the super-cooled cloud droplets and very small ice crystals upward. At the same time, the graupel, which is considerably larger and denser, tends to fall or be suspended in the rising air. The differences in

7480-399: The data that the energy emitted is reduced for wavelengths less than the wavelength of the observed peak of emission. Notice that there are two factors responsible for the shape of the graph, which can be seen as working opposite to one another. Firstly, shorter wavelengths have a larger number of modes associated with them. This accounts for the increase in spectral radiance as one moves from

7590-519: The decrease in spectral radiance at very short wavelengths, left of the peak. Combined, they give the characteristic graph. Calculating the blackbody curve was a major challenge in theoretical physics during the late nineteenth century. The problem was solved in 1901 by Max Planck in the formalism now known as Planck's law of blackbody radiation. By making changes to Wien's radiation law (not to be confused with Wien's displacement law) consistent with thermodynamics and electromagnetism , he found

7700-523: The emissivity is a constant. This is known as the gray body assumption. With non-black surfaces, the deviations from ideal blackbody behavior are determined by both the surface structure, such as roughness or granularity, and the chemical composition. On a "per wavelength" basis, real objects in states of local thermodynamic equilibrium still follow Kirchhoff's Law : emissivity equals absorptivity, so that an object that does not absorb all incident light will also emit less radiation than an ideal black body;

7810-428: The emitted radiation at a given frequency is a fraction of what the ideal emission would be. The emissivity of a material specifies how well a real body radiates energy as compared with a black body. This emissivity depends on factors such as temperature, emission angle, and wavelength. However, it is typical in engineering to assume that a surface's spectral emissivity and absorptivity do not depend on wavelength so that

7920-425: The energy emitted tends to infinity, hence the ultraviolet catastrophe. The theory even predicted that all bodies would emit most of their energy in the ultraviolet range, clearly contradicted by the experimental data which showed a different peak wavelength at different temperatures (see also Wien's law ). Instead, in the quantum treatment of this problem, the numbers of the energy modes are quantized , attenuating

8030-456: The energy they emit. The term black body was introduced by Gustav Kirchhoff in 1860. Blackbody radiation is also called thermal radiation , cavity radiation , complete radiation or temperature radiation . Black-body radiation has a characteristic, continuous frequency spectrum that depends only on the body's temperature, called the Planck spectrum or Planck's law . The spectrum

8140-562: The foundations of quantum mechanics . According to the Classical Theory of Radiation, if each Fourier mode of the equilibrium radiation (in an otherwise empty cavity with perfectly reflective walls) is considered as a degree of freedom capable of exchanging energy, then, according to the equipartition theorem of classical physics, there would be an equal amount of energy in each mode. Since there are an infinite number of modes, this would imply infinite heat capacity , as well as

8250-456: The ground and tops up to 15 km (9.3 mi) in height. The place on Earth where lightning occurs most often is over Lake Maracaibo , wherein the Catatumbo lightning phenomenon produces 250 bolts of lightning a day. This activity occurs on average, 297 days a year. The second most lightning density is near the village of Kifuka in the mountains of the eastern Democratic Republic of

8360-495: The ground, the proportion of CG strikes (versus CC or IC discharges) becomes greater when the cloud is closer to the ground. In the tropics, where the freezing level is generally higher in the atmosphere, only 10% of lightning flashes are CG. At the latitude of Norway (around 60° North latitude), where the freezing elevation is lower, 50% of lightning is CG. Lightning is usually produced by cumulonimbus clouds, which have bases that are typically 1–2 km (0.62–1.24 mi) above

8470-405: The ground. Called step potentials, they are responsible for more injuries and deaths in groups of people or of other animals than the strike itself. Electricity takes every path available to it. Such step potentials will often cause current to flow through one leg and out another, electrocuting an unlucky human or animal standing near the point where the lightning strikes. The electric current of

8580-487: The hole at each wavelength) will be continuous, and will depend only on the temperature and the fact that the walls are opaque and at least partly absorptive, but not on the particular material of which they are built nor on the material in the cavity (compare with emission spectrum ). The radiance or observed intensity is not a function of direction. Therefore, a black body is a perfect Lambertian radiator. Real objects never behave as full-ideal black bodies, and instead

8690-421: The hole is small enough to have a negligible effect upon the equilibrium. The thermal radiation spontaneously emitted by many ordinary objects can be approximated as blackbody radiation. Of particular importance, although planets and stars (including the Earth and Sun ) are neither in thermal equilibrium with their surroundings nor perfect black bodies, blackbody radiation is still a good first approximation for

8800-405: The incomplete absorption can be due to some of the incident light being transmitted through the body or to some of it being reflected at the surface of the body. In astronomy , objects such as stars are frequently regarded as black bodies, though this is often a poor approximation. An almost perfect blackbody spectrum is exhibited by the cosmic microwave background radiation . Hawking radiation

8910-460: The infrared (IR) portion of the spectrum. In this frequency range, it emits ϵ ¯ {\displaystyle {\overline {\epsilon }}} of the radiation that a black body would emit where ϵ ¯ {\displaystyle {\overline {\epsilon }}} is the average emissivity in the IR range. The power emitted by the planet is then: For

9020-403: The initial return stroke. Each subsequent stroke usually re-uses the discharge channel taken by the previous one, but the channel may be offset from its previous position as wind displaces the hot channel. Black-body radiation A perfectly insulated enclosure which is in thermal equilibrium internally contains blackbody radiation, and will emit it through a hole made in its wall, provided

9130-438: The ionic channel takes a comparatively long amount of time (hundreds of milliseconds ) in comparison to the resulting discharge, which occurs within a few dozen microseconds. The electric current needed to establish the channel, measured in the tens or hundreds of amperes , is dwarfed by subsequent currents during the actual discharge. Initiation of the lightning leader is not well understood. The electric field strength within

9240-408: The leaders can be readily observed in slow-motion videos of lightning flashes. It is possible for one end of the leader to fill the oppositely-charged well entirely while the other end is still active. When this happens, the leader end which filled the well may propagate outside of the thundercloud and result in either a cloud-to-air flash or a cloud-to-ground flash. In a typical cloud-to-ground flash,

9350-449: The longest wavelengths towards the peak at relatively shorter wavelengths. Secondly, though, at shorter wavelengths more energy is needed to reach the threshold level to occupy each mode: the more energy needed to excite the mode, the lower the probability that this mode will be occupied. As the wavelength decreases, the probability of exciting the mode becomes exceedingly small, leading to fewer of these modes being occupied: this accounts for

9460-436: The lower part of the storm. The result is that the upper part of the thunderstorm cloud becomes positively charged while the middle to lower part of the thunderstorm cloud becomes negatively charged. The upward motions within the storm and winds at higher levels in the atmosphere tend to cause the small ice crystals (and positive charge) in the upper part of the thunderstorm cloud to spread out horizontally some distance from

9570-1662: The maximum intensity is for ν {\displaystyle \nu } = 17 THz . By integrating B ν ( T ) cos ⁡ ( θ ) {\displaystyle B_{\nu }(T)\cos(\theta )} over the frequency the radiance L {\displaystyle L} (units: power / [area × solid angle] ) is L = 2 π 5 15 k 4 T 4 c 2 h 3 1 π = σ T 4 cos ⁡ ( θ ) π {\displaystyle L={\frac {2\pi ^{5}}{15}}{\frac {k^{4}T^{4}}{c^{2}h^{3}}}{\frac {1}{\pi }}=\sigma T^{4}{\frac {\cos(\theta )}{\pi }}} by using ∫ 0 ∞ d x x 3 e x − 1 = π 4 15 {\displaystyle \int _{0}^{\infty }dx\,{\frac {x^{3}}{e^{x}-1}}={\frac {\pi ^{4}}{15}}} with x ≡ h ν k T {\displaystyle x\equiv {\frac {h\nu }{kT}}} and with σ ≡ 2 π 5 15 k 4 c 2 h 3 = 5.670373 × 10 − 8 W m 2 K 4 {\displaystyle \sigma \equiv {\frac {2\pi ^{5}}{15}}{\frac {k^{4}}{c^{2}h^{3}}}=5.670373\times 10^{-8}\mathrm {\frac {W}{m^{2}K^{4}}} } being

9680-431: The maximum occurs when e x ( 1 − x / 3 ) = 1 {\displaystyle e^{x}(1-x/3)=1} , where x = h ν / k T {\displaystyle x=h\nu /kT} . The approximate numerical solution is x ≈ 2.82 {\displaystyle x\approx 2.82} . At a typical room temperature of 293 K (20 °C),

9790-416: The movement of the precipitation cause collisions to occur. When the rising ice crystals collide with graupel, the ice crystals become positively charged and the graupel becomes negatively charged; see Figure 2. The updraft carries the positively charged ice crystals upward toward the top of the storm cloud. The larger and denser graupel is either suspended in the middle of the thunderstorm cloud or falls toward

9900-426: The negative leader's connection with the ground. Positive leaders decay more rapidly than negative leaders do. For reasons not well understood, bidirectional leaders tend to initiate on the tips of the decayed positive leaders in which the negative end attempts to re-ionize the leader network. These leaders, also called recoil leaders , usually decay shortly after their formation. When they do manage to make contact with

10010-457: The planet is hit with only a tiny fraction of it. The power from the Sun that strikes the planet (at the top of the atmosphere) is: where Because of its high temperature, the Sun emits to a large extent in the ultraviolet and visible (UV-Vis) frequency range. In this frequency range, the planet reflects a fraction α {\displaystyle \alpha } of this energy where α {\displaystyle \alpha }

10120-442: The radiation is strongest is given by Wien's displacement law, and the overall power emitted per unit area is given by the Stefan–Boltzmann law . So, as temperature increases, the glow color changes from red to yellow to white to blue. Even as the peak wavelength moves into the ultra-violet, enough radiation continues to be emitted in the blue wavelengths that the body will continue to appear blue. It will never become invisible—indeed,

10230-400: The radiation of visible light increases monotonically with temperature. The Stefan–Boltzmann law also says that the total radiant heat energy emitted from a surface is proportional to the fourth power of its absolute temperature . The law was formulated by Josef Stefan in 1879 and later derived by Ludwig Boltzmann. The formula E = σT is given, where E is the radiant heat emitted from

10340-480: The receiving surface is perpendicular to the radiation. By subsequently integrating L {\displaystyle L} over the solid angle Ω {\displaystyle \Omega } for all azimuthal angle (0 to 2 π {\displaystyle 2\pi } ) and polar angle θ {\displaystyle \theta } from 0 to π / 2 {\displaystyle \pi /2} , we arrive at

10450-470: The return stroke averages 30 kiloamperes for a typical negative CG flash, often referred to as "negative CG" lightning. In some cases, a ground-to-cloud (GC) lightning flash may originate from a positively charged region on the ground below a storm. These discharges normally originate from the tops of very tall structures, such as communications antennas. The rate at which the return stroke current travels has been found to be around 100,000 km/s (one-third of

10560-513: The same term [REDACTED] This disambiguation page lists articles associated with the title Inazuma . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Inazuma&oldid=1179823699 " Categories : Disambiguation pages Disambiguation pages with surname-holder lists Hidden categories: Articles containing Japanese-language text Short description

10670-545: The southern U.S.—sixty km (37 mi) longer than the previous distance record (southern Brazil, October 31, 2018). A single flash in Uruguay and northern Argentina on June 18, 2020, lasted for 17.1 seconds—0.37 seconds longer than the previous record (March 4, 2019, also in northern Argentina). In order for an electrostatic discharge to occur, two preconditions are necessary: first, a sufficiently high potential difference between two regions of space must exist, and second,

10780-452: The spectrum at high frequency in agreement with experimental observation and resolving the catastrophe. The modes that had more energy than the thermal energy of the substance itself were not considered, and because of quantization modes having infinitesimally little energy were excluded. Thus for shorter wavelengths very few modes (having energy more than h ν {\displaystyle h\nu } ) were allowed, supporting

10890-404: The speed of light). The massive flow of electric current occurring during the return stroke combined with the rate at which it occurs (measured in microseconds) rapidly superheats the completed leader channel, forming a highly electrically conductive plasma channel. The core temperature of the plasma during the return stroke may exceed 27,800 °C (50,000 °F), causing it to radiate with

11000-413: The speed of light. This is the "return stroke" and it is the most luminous and noticeable part of the lightning discharge. A large electric charge flows along the plasma channel, from the cloud to the ground, neutralising the positive ground charge as electrons flow away from the strike point to the surrounding area. This huge surge of current creates large radial voltage differences along the surface of

11110-435: The spherical surface area being 4 π R 2 {\displaystyle 4\pi R^{2}} . If the planet were a perfect black body, it would emit according to the Stefan–Boltzmann law where T E {\displaystyle T_{\rm {E}}} is the temperature of the planet. This temperature, calculated for the case of the planet acting as a black body by setting P

11220-427: The superseding of classical electromagnetism by quantum electrodynamics . These quanta were called photons and the blackbody cavity was thought of as containing a gas of photons . In addition, it led to the development of quantum probability distributions, called Fermi–Dirac statistics and Bose–Einstein statistics , each applicable to a different class of particles, fermions and bosons . The wavelength at which

11330-468: The surface temperature to about 28 °C when the ambient temperature is 20 °C. Hence, the net radiative heat loss is about P net = P emit − P absorb = 100   W . {\displaystyle P_{\text{net}}=P_{\text{emit}}-P_{\text{absorb}}=\mathrm {100~W} .} The total energy radiated in one day is about 8 MJ , or 2000 kcal (food calories ). Basal metabolic rate for

11440-566: The thundercloud is not typically large enough to initiate this process by itself. Many hypotheses have been proposed. One hypothesis postulates that showers of relativistic electrons are created by cosmic rays and are then accelerated to higher velocities via a process called runaway breakdown . As these relativistic electrons collide and ionize neutral air molecules, they initiate leader formation. Another hypothesis involves locally enhanced electric fields being formed near elongated water droplets or ice crystals. Percolation theory , especially for

11550-495: The thunderstorm cloud base. This part of the thunderstorm cloud is called the anvil. While this is the main charging process for the thunderstorm cloud, some of these charges can be redistributed by air movements within the storm (updrafts and downdrafts). In addition, there is a small but important positive charge buildup near the bottom of the thunderstorm cloud due to the precipitation and warmer temperatures. The induced separation of charge in pure liquid water has been known since

11660-435: The time scales involved in thunderstorms. The charge carrier in lightning is mainly electrons in a plasma. The process of going from charge as ions (positive hydrogen ion and negative hydroxide ion) associated with liquid water or solid water to charge as electrons associated with lightning must involve some form of electro-chemistry, that is, the oxidation and/or the reduction of chemical species. As hydroxide functions as

11770-406: The topographic variation that would result in atmospheric mixing, lightning is notably less frequent over the world's oceans than over land. The North and South Poles are limited in their coverage of thunderstorms and therefore result in areas with the least lightning. In general, CG lightning flashes account for only 25% of all total lightning flashes worldwide. Since the base of a thunderstorm

11880-559: The type. This discharge may produce a wide range of electromagnetic radiation , from heat created by the rapid movement of electrons , to brilliant flashes of visible light in the form of black-body radiation . Lightning causes thunder , a sound from the shock wave which develops as gases in the vicinity of the discharge experience a sudden increase in pressure. Lightning occurs commonly during thunderstorms as well as other types of energetic weather systems, but volcanic lightning can also occur during volcanic eruptions . Lightning

11990-489: The ultimately stable steady state equilibrium radiation in a cavity in a rigid body, at a uniform temperature, that is entirely opaque and is only partly reflective. A closed box with walls of graphite at a constant temperature with a small hole on one side produces a good approximation to ideal blackbody radiation emanating from the opening. Blackbody radiation has the unique absolutely stable distribution of radiative intensity that can persist in thermodynamic equilibrium in

12100-417: The wall of a large uniformly heated opaque-walled cavity (such as an oven), viewed from outside, looks red; at 6000 K , it looks white. No matter how the oven is constructed, or of what material, as long as it is built so that almost all light entering is absorbed by its walls, it will contain a good approximation to blackbody radiation. The spectrum, and therefore color, of the light that comes out will be

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