1.
Daylighting
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Daylighting is the practice of placing windows or other openings and reflective surfaces so that during the day natural light provides effective internal lighting. Particular attention is given to daylighting while designing a building when the aim is to maximize visual comfort or to reduce energy use, Energy savings can be achieved from the reduced use of artificial lighting or from passive solar heating. Daylighting is a term given to a common centuries-old, geography. The amount of daylight received in a space can be analyzed by measuring illuminance on a grid or undertaking a daylight factor calculation. Today, the use of software, such as Radiance, can allow an architect or engineer to quickly undertake complex calculations to review the benefit of a particular design, the source of all daylight is the sun. The proportion of direct to diffuse light impacts the amount and quality of daylight, solar radiation that reaches a site without being scattered within the earth’s atmosphere is called direct sunlight. In contrast, light that is scattered in the atmosphere is referred to as diffused daylight, ground reflected light also contributes to the daylight. Each climate has different composition of these daylights and different cloud coverage, so daylighting strategies vary with site locations, traditionally, houses were designed with minimal windows on the polar side but more and larger windows on the equatorial-side. Equatorial-side windows receive at least some direct sunlight on any day of the year so they are effective at daylighting areas of the house adjacent to the windows. Even so, during mid-winter, light incidence is highly directional and this may be partially ameliorated through light diffusion, light pipes or tubes, and through somewhat reflective internal surfaces. In fairly low latitudes in summertime, windows that face east and west, windows are the most common way to admit daylight into a space. Their vertical orientation means that they selectively admit sunlight and diffuse daylight at different times of the day, therefore, windows on multiple orientations must usually be combined to produce the right mix of light for the building, depending on the climate and latitude. Different types and grades of glass and different window treatments can also affect the amount of transmission through the windows. The type of glazing is an important issue, expressed by its VT coefficient, as the name suggests, this coefficient measures how much visible light is admitted by the window. A low VT can reduce by half or more the coming into a room. But be also aware of high VT glass, high VT numbers can be a cause of glare, on the other hand, you should also take into account the undesirable effects of large windows. Another important element in creating daylighting is the use of clerestory windows and these are high, vertically placed windows. They can be used to increase direct solar gain when oriented towards the equator, when facing toward the sun, clerestories and other windows may admit unacceptable glare
2.
Solar irradiance
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Solar irradiance is the power per unit area received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Irradiance may be measured in space or at the Earths surface after atmospheric absorption and it is measured perpendicular to the incoming sunlight. Total solar irradiance, is a measure of the power over all wavelengths per unit area incident on the Earths upper atmosphere. The solar constant is a measure of mean TSI at a distance of one astronomical Unit. Irradiance is a function of distance from the Sun, the solar cycle, Irradiance on Earth is also measured perpendicular to the incoming sunlight. Insolation is the received on Earth per unit area on a horizontal surface. It depends on the height of the Sun above the horizon, the solar irradiance integrated over time is called solar irradiation, solar exposure or insolation. However, insolation is often used interchangeably with irradiance in practice, the SI unit of irradiance is watt per square meter. An alternate unit of measure is the Langley per unit time, the solar energy industry uses watt-hour per square metre per unit time, the relation to the SI unit is thus 1 kW/m2 =24 kWh/m2/day =8760 kWh/m2/year. Irradiance can also be expressed in Suns, where one Sun equals 1000 W/m2 at the point of arrival, part of the radiation reaching an object is absorbed and the remainder reflected. Usually the absorbed radiation is converted to energy, increasing the objects temperature. Manmade or natural systems, however, can convert part of the radiation into another form such as electricity or chemical bonds. The proportion of reflected radiation is the objects reflectivity or albedo, insolation onto a surface is largest when the surface directly faces the sun. As the angle between the surface and the Sun moves from normal, the insolation is reduced in proportion to the angles cosine, see effect of sun angle on climate. In the figure, the angle shown is between the ground and the rather than between the vertical direction and the sunbeam, hence the sine rather than the cosine is appropriate. A sunbeam one mile wide arrives from directly overhead, and another at a 30° angle to the horizontal, the sine of a 30° angle is 1/2, whereas the sine of a 90° angle is 1. Therefore, the angled sunbeam spreads the light over twice the area, consequently, half as much light falls on each square mile. This projection effect is the reason why Earths polar regions are much colder than equatorial regions
3.
Crepuscular rays
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Crepuscular rays /krᵻˈpʌskjᵿlər/, in atmospheric optics, are rays of sunlight that appear to radiate from the point in the sky where the sun is located. These rays, which stream through gaps in clouds or between other objects, are columns of sunlit air separated by darker cloud-shadowed regions, despite seeming to converge at a point, the rays are in fact near-parallel shafts of sunlight, and their apparent convergence is a perspective effect. The name comes from their frequent occurrences during twilight hours, when the contrasts between light and dark are the most obvious, crepuscular comes from the Latin word crepusculum, meaning twilight. The rays in some cases may extend across the sky and appear to converge at the antisolar point, in this case they are called anticrepuscular or antisolar rays. These are not as easily spotted as crepuscular rays and this apparent dual convergence is a perspective effect analogous to railway tracks appearing to converge to opposite points in opposite directions. Crepuscular rays are usually orange in appearance because the path through the atmosphere at sunrise, particles in the air scatter short wavelength light through Rayleigh scattering much more strongly than longer wavelength yellow and red light. Backstays of the nautical term, from the fact that backstays that brace the mast of a sailing ship converge in a similar way Buddha rays Cloud breaks Jacobs Ladder Ropes of Maui—originally
4.
Electromagnetic radiation
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In physics, electromagnetic radiation refers to the waves of the electromagnetic field, propagating through space carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, light, ultraviolet, X-, classically, electromagnetic radiation consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields that propagate at the speed of light through a vacuum. The oscillations of the two fields are perpendicular to other and perpendicular to the direction of energy and wave propagation. The wavefront of electromagnetic waves emitted from a point source is a sphere, the position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength. Electromagnetic waves are produced whenever charged particles are accelerated, and these waves can interact with other charged particles. EM waves carry energy, momentum and angular momentum away from their source particle, quanta of EM waves are called photons, whose rest mass is zero, but whose energy, or equivalent total mass, is not zero so they are still affected by gravity. Thus, EMR is sometimes referred to as the far field, in this language, the near field refers to EM fields near the charges and current that directly produced them, specifically, electromagnetic induction and electrostatic induction phenomena. In the quantum theory of electromagnetism, EMR consists of photons, quantum effects provide additional sources of EMR, such as the transition of electrons to lower energy levels in an atom and black-body radiation. The energy of a photon is quantized and is greater for photons of higher frequency. This relationship is given by Plancks equation E = hν, where E is the energy per photon, ν is the frequency of the photon, a single gamma ray photon, for example, might carry ~100,000 times the energy of a single photon of visible light. The effects of EMR upon chemical compounds and biological organisms depend both upon the power and its frequency. EMR of visible or lower frequencies is called non-ionizing radiation, because its photons do not individually have enough energy to ionize atoms or molecules, the effects of these radiations on chemical systems and living tissue are caused primarily by heating effects from the combined energy transfer of many photons. In contrast, high ultraviolet, X-rays and gamma rays are called ionizing radiation since individual photons of high frequency have enough energy to ionize molecules or break chemical bonds. These radiations have the ability to cause chemical reactions and damage living cells beyond that resulting from simple heating, Maxwell derived a wave form of the electric and magnetic equations, thus uncovering the wave-like nature of electric and magnetic fields and their symmetry. Because the speed of EM waves predicted by the wave equation coincided with the speed of light. Maxwell’s equations were confirmed by Heinrich Hertz through experiments with radio waves, according to Maxwells equations, a spatially varying electric field is always associated with a magnetic field that changes over time. Likewise, a varying magnetic field is associated with specific changes over time in the electric field. In an electromagnetic wave, the changes in the field are always accompanied by a wave in the magnetic field in one direction
5.
Sun
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The Sun is the star at the center of the Solar System. It is a perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99. 86% of the total mass of the Solar System. About three quarters of the Suns mass consists of hydrogen, the rest is mostly helium, with smaller quantities of heavier elements, including oxygen, carbon, neon. The Sun is a G-type main-sequence star based on its spectral class and it formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into a disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core and it is thought that almost all stars form by this process. The Sun is roughly middle-aged, it has not changed dramatically for more than four billion years and it is calculated that the Sun will become sufficiently large enough to engulf the current orbits of Mercury, Venus, and probably Earth. The enormous effect of the Sun on Earth has been recognized since prehistoric times, the synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today. The English proper name Sun developed from Old English sunne and may be related to south, all Germanic terms for the Sun stem from Proto-Germanic *sunnōn. The English weekday name Sunday stems from Old English and is ultimately a result of a Germanic interpretation of Latin dies solis, the Latin name for the Sun, Sol, is not common in general English language use, the adjectival form is the related word solar. The term sol is used by planetary astronomers to refer to the duration of a solar day on another planet. A mean Earth solar day is approximately 24 hours, whereas a mean Martian sol is 24 hours,39 minutes, and 35.244 seconds. From at least the 4th Dynasty of Ancient Egypt, the Sun was worshipped as the god Ra, portrayed as a falcon-headed divinity surmounted by the solar disk, and surrounded by a serpent. In the New Empire period, the Sun became identified with the dung beetle, in the form of the Sun disc Aten, the Sun had a brief resurgence during the Amarna Period when it again became the preeminent, if not only, divinity for the Pharaoh Akhenaton. The Sun is viewed as a goddess in Germanic paganism, Sól/Sunna, in ancient Roman culture, Sunday was the day of the Sun god. It was adopted as the Sabbath day by Christians who did not have a Jewish background, the symbol of light was a pagan device adopted by Christians, and perhaps the most important one that did not come from Jewish traditions
6.
Infrared
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It extends from the nominal red edge of the visible spectrum at 700 nanometers, to 1000000 nm. Most of the radiation emitted by objects near room temperature is infrared. Like all EMR, IR carries radiant energy, and behaves both like a wave and like its quantum particle, the photon, slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has an effect on Earths climate. Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements and it excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines absorption and transmission of photons in the infrared range, Infrared radiation is used in industrial, scientific, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected, Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatuses. Thermal-infrared imaging is used extensively for military and civilian purposes, military applications include target acquisition, surveillance, night vision, homing, and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm, Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers to 1 mm. This range of wavelengths corresponds to a range of approximately 430 THz down to 300 GHz. Below infrared is the portion of the electromagnetic spectrum. Sunlight, at a temperature of 5,780 kelvins, is composed of near thermal-spectrum radiation that is slightly more than half infrared. At zenith, sunlight provides an irradiance of just over 1 kilowatt per square meter at sea level, of this energy,527 watts is infrared radiation,445 watts is visible light, and 32 watts is ultraviolet radiation. Nearly all the radiation in sunlight is near infrared, shorter than 4 micrometers. On the surface of Earth, at far lower temperatures than the surface of the Sun, almost all thermal radiation consists of infrared in mid-infrared region, much longer than in sunlight. Of these natural thermal radiation processes only lightning and natural fires are hot enough to produce much visible energy, thermal infrared radiation also has a maximum emission wavelength, which is inversely proportional to the absolute temperature of object, in accordance with Wiens displacement law. Therefore, the band is often subdivided into smaller sections. Due to the nature of the blackbody radiation curves, typical hot objects, such as exhaust pipes, the three regions are used for observation of different temperature ranges, and hence different environments in space
7.
Light
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Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to light, which is visible to the human eye and is responsible for the sense of sight. Visible light is defined as having wavelengths in the range of 400–700 nanometres, or 4.00 × 10−7 to 7.00 × 10−7 m. This wavelength means a range of roughly 430–750 terahertz. The main source of light on Earth is the Sun, sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of photosynthesis provides virtually all the used by living things. Historically, another important source of light for humans has been fire, with the development of electric lights and power systems, electric lighting has effectively replaced firelight. Some species of animals generate their own light, a process called bioluminescence, for example, fireflies use light to locate mates, and vampire squids use it to hide themselves from prey. Visible light, as all types of electromagnetic radiation, is experimentally found to always move at this speed in a vacuum. In physics, the term sometimes refers to electromagnetic radiation of any wavelength. In this sense, gamma rays, X-rays, microwaves and radio waves are also light, like all types of light, visible light is emitted and absorbed in tiny packets called photons and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality, the study of light, known as optics, is an important research area in modern physics. Generally, EM radiation, or EMR, is classified by wavelength into radio, microwave, infrared, the behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths, when EMR interacts with single atoms and molecules, its behavior depends on the amount of energy per quantum it carries. There exist animals that are sensitive to various types of infrared, infrared sensing in snakes depends on a kind of natural thermal imaging, in which tiny packets of cellular water are raised in temperature by the infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detect it, above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nanometers and the internal lens below 400. Furthermore, the rods and cones located in the retina of the eye cannot detect the very short ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses are able to detect ultraviolet, by quantum photon-absorption mechanisms, various sources define visible light as narrowly as 420 to 680 to as broadly as 380 to 800 nm
8.
Ultraviolet
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Ultraviolet is an electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation constitutes about 10% of the light output of the Sun. It is also produced by electric arcs and specialized lights, such as lamps, tanning lamps. Consequently, the effects of UV are greater than simple heating effects. Suntan, freckling and sunburn are familiar effects of over-exposure, along with risk of skin cancer. Living things on dry land would be damaged by ultraviolet radiation from the Sun if most of it were not filtered out by the Earths atmosphere. More-energetic, shorter-wavelength extreme UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground, Ultraviolet is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates, including humans. The UV spectrum thus has both beneficial and harmful to human health. Ultraviolet rays are invisible to most humans, the lens in a human eye ordinarily filters out UVB frequencies or higher, and humans lack color receptor adaptations for ultraviolet rays. Under some conditions, children and young adults can see ultraviolet down to wavelengths of about 310 nm, near-UV radiation is visible to some insects, mammals, and birds. Small birds have a fourth color receptor for ultraviolet rays, this gives birds true UV vision, reindeer use near-UV radiation to see polar bears, who are poorly visible in regular light because they blend in with the snow. UV also allows mammals to see urine trails, which is helpful for animals to find food in the wild. The males and females of some species look identical to the human eye. Ultraviolet means beyond violet, violet being the color of the highest frequencies of visible light, Ultraviolet has a higher frequency than violet light. He called them oxidizing rays to emphasize chemical reactivity and to them from heat rays. The terms chemical and heat rays were eventually dropped in favour of ultraviolet and infrared radiation, in 1878 the effect of short-wavelength light on sterilizing bacteria was discovered. By 1903 it was known the most effective wavelengths were around 250 nm, in 1960, the effect of ultraviolet radiation on DNA was established. The discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet because it is absorbed by air, was made in 1893 by the German physicist Victor Schumann
9.
Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
10.
Optical filter
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Filters mostly belong to one of two categories. The simplest, physically, is the filter, then there are interference or dichroic filters. Optical filters selectively transmit light in a range of wavelengths. They can usually pass long wavelengths only, short wavelengths only, or a band of wavelengths, the passband may be narrower or wider, the transition or cutoff between maximal and minimal transmission can be sharp or gradual. Optical filters are used in photography, in many optical instruments. Optical filters are essential in fluorescence applications such as fluorescence microscopy. Photographic filters are a case of optical filters, and much of the material here applies. Some photographic effect filters, such as star effect filters, are not relevant to scientific work, absorptive filters are usually made from glass to which various inorganic or organic compounds have been added. These compounds absorb some wavelengths of light while transmitting others, the compounds can also be added to plastic to produce gel filters, which are lighter and cheaper than glass-based filters. Alternately, dichroic filters can be made by coating a substrate with a series of optical coatings. Dichroic filters usually reflect the unwanted portion of the light and transmit the remainder, Dichroic filters use the principle of interference. Their layers form a series of reflective cavities that resonate with the desired wavelengths. Other wavelengths destructively cancel or reflect as the peaks and troughs of the waves overlap, Dichroic filters are particularly suited for precise scientific work, since their exact colour range can be controlled by the thickness and sequence of the coatings. They are usually more expensive and delicate than absorption filters. They can be used in such as the dichroic prism of a camera to separate a beam of light into different coloured components. The basic scientific instrument of this type is a Fabry–Pérot interferometer and it uses two mirrors to establish a resonating cavity. It passes wavelengths that are a multiple of the resonance frequency. Etalons are another variation, transparent cubes or fibers whose polished ends form mirrors tuned to resonate with specific wavelengths and these are often used to separate channels in telecommunications networks that use wavelength division multiplexing on long-haul optic fibers
11.
Atmosphere of Earth
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The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earths gravity. The atmosphere of Earth protects life on Earth by absorbing solar radiation, warming the surface through heat retention. By volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor, on average around 1% at sea level. The atmosphere has a mass of about 5. 15×1018 kg, the atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km, or 1. 57% of Earths radius, is used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km, several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earths atmosphere and its processes is called atmospheric science, early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The three major constituents of air, and therefore of Earths atmosphere, are nitrogen, oxygen, water vapor accounts for roughly 0. 25% of the atmosphere by mass. The remaining gases are often referred to as gases, among which are the greenhouse gases, principally carbon dioxide, methane, nitrous oxide. Filtered air includes trace amounts of other chemical compounds. Various industrial pollutants also may be present as gases or aerosols, such as chlorine, fluorine compounds, sulfur compounds such as hydrogen sulfide and sulfur dioxide may be derived from natural sources or from industrial air pollution. In general, air pressure and density decrease with altitude in the atmosphere, however, temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions. In this way, Earths atmosphere can be divided into five main layers, excluding the exosphere, Earth has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. It extends from the exobase, which is located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km where it merges into the solar wind. This layer is composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen. The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another, thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind, the exosphere is located too far above Earth for any meteorological phenomena to be possible
12.
Daylight
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Daylight, or the light of day, is the combination of all direct and indirect sunlight during the daytime. This includes direct sunlight, diffuse sky radiation, and both of these reflected from the Earth and terrestrial objects, sunlight scattered or reflected from objects in outer space is not generally considered daylight. Thus, moonlight is never considered daylight, despite being indirect sunlight, daytime is the period of time each day when daylight occurs. Daylight happens because the Earth rotates and either side the sun shines on is considered daylight, daylight is present at a particular location, to some degree, whenever the sun is above the horizon at that location. It may be darker under unusual circumstances such as an eclipse or very high levels of atmospheric smoke, dust. For comparison, nighttime levels are, For a table of approximate daylight intensity in the Solar System. Daylighting is lighting an indoor space with such as windows. This type of lighting is chosen to save energy, to avoid hypothesized adverse health effects of over-illumination by artificial light, the amount of daylight received into an indoor space or room is defined as a daylight factor, being the ratio between the measured internal and external light levels. In recent years, work has taken place to recreate the effects of daylight artificially and this is however expensive in terms of both equipment and energy consumption and is applied almost exclusively in specialist areas such as filmmaking, where light of such intensity is required anyway. In some filmmaking locations, such as Sweden, there is too much light due to summer days. As a result, in films like Marianne, night scenes have to be shot during the daylight hours. Http, //www. gandraxa. com/length_of_day. xml Deriving the formulas to calculate the length of day
13.
Horizon
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At many locations, the true horizon is obscured by trees, buildings, mountains, etc. and the resulting intersection of earth and sky is called the visible horizon. When looking at a sea from a shore, the part of the sea closest to the horizon is called the offing. The word horizon derives from the Greek ὁρίζων κύκλος horizōn kyklos, separating circle, from the verb ὁρίζω horizō, to divide, to separate, a pilot can also retain his or her spatial orientation by referring to the horizon. For observers near sea level the difference between this geometrical horizon and the horizon is imperceptible to the naked eye. In astronomy the horizon is the plane through the eyes of the observer. It is the plane of the horizontal coordinate system, the locus of points that have an altitude of zero degrees. While similar in ways to the horizon, in this context a horizon may be considered to be a plane in space. One typically sees further along the Earths curved surface than a simple geometric calculation allows for because of refraction error, the reverse happens if the ground is hotter than the air above it, as often happens in deserts, producing mirages. Examples, For an observer standing on the ground with h =1.70 metres, for an observer standing on the ground with h =2 metres, the horizon is at a distance of 5 kilometres. For an observer standing on a hill or tower of 100 metres in height, for an observer standing at the top of the Burj Khalifa, the horizon is at a distance of 103 kilometres. For an observer atop Mount Everest, the horizon is at a distance of 336 kilometres, with d in miles and h in feet, d ≈1.5 h ≈1.22 h. Examples, assuming no refraction, For an observer on the ground with eye level at h =5 ft 7 in, for an observer standing on a hill or tower 100 feet in height, the horizon is at a distance of 12.2 miles. For an observer on the summit of Aconcagua, the horizon to the west is at a distance of 184 miles. The secant-tangent theorem states that O C2 = O A × O B, the equation can also be derived using the Pythagorean theorem. Since the line of sight is a tangent to the Earth and this sets up a right triangle, with the sum of the radius and the height as the hypotenuse. Another relationship involves the distance s along the surface of the Earth to the horizon, with γ in radians, s = R γ. Solving for s gives s = R cos −1 R R + h, the distances d and s are nearly the same when the height of the object is negligible compared to the radius. If the observer is close to the surface of the earth, then it is valid to disregard h in the term, and the formula becomes d =2 R h
14.
Solar radiation
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Solar irradiance is the power per unit area received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Irradiance may be measured in space or at the Earths surface after atmospheric absorption and it is measured perpendicular to the incoming sunlight. Total solar irradiance, is a measure of the power over all wavelengths per unit area incident on the Earths upper atmosphere. The solar constant is a measure of mean TSI at a distance of one astronomical Unit. Irradiance is a function of distance from the Sun, the solar cycle, Irradiance on Earth is also measured perpendicular to the incoming sunlight. Insolation is the received on Earth per unit area on a horizontal surface. It depends on the height of the Sun above the horizon, the solar irradiance integrated over time is called solar irradiation, solar exposure or insolation. However, insolation is often used interchangeably with irradiance in practice, the SI unit of irradiance is watt per square meter. An alternate unit of measure is the Langley per unit time, the solar energy industry uses watt-hour per square metre per unit time, the relation to the SI unit is thus 1 kW/m2 =24 kWh/m2/day =8760 kWh/m2/year. Irradiance can also be expressed in Suns, where one Sun equals 1000 W/m2 at the point of arrival, part of the radiation reaching an object is absorbed and the remainder reflected. Usually the absorbed radiation is converted to energy, increasing the objects temperature. Manmade or natural systems, however, can convert part of the radiation into another form such as electricity or chemical bonds. The proportion of reflected radiation is the objects reflectivity or albedo, insolation onto a surface is largest when the surface directly faces the sun. As the angle between the surface and the Sun moves from normal, the insolation is reduced in proportion to the angles cosine, see effect of sun angle on climate. In the figure, the angle shown is between the ground and the rather than between the vertical direction and the sunbeam, hence the sine rather than the cosine is appropriate. A sunbeam one mile wide arrives from directly overhead, and another at a 30° angle to the horizontal, the sine of a 30° angle is 1/2, whereas the sine of a 90° angle is 1. Therefore, the angled sunbeam spreads the light over twice the area, consequently, half as much light falls on each square mile. This projection effect is the reason why Earths polar regions are much colder than equatorial regions
15.
Radiant heat
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Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a greater than absolute zero emits thermal radiation. When the temperature of a body is greater than absolute zero, Thermal radiation is different from thermal convection and thermal conduction—a person near a raging bonfire feels radiant heating from the fire, even if the surrounding air is very cold. Sunlight is part of thermal radiation generated by the hot plasma of the Sun, the Earth also emits thermal radiation, but at a much lower intensity and different spectral distribution because it is cooler. The Earths absorption of radiation, followed by its outgoing thermal radiation are the two most important processes that determine the temperature and climate of the Earth. If a radiation-emitting object meets the physical characteristics of a body in thermodynamic equilibrium. Plancks law describes the spectrum of radiation, which depends only on the objects temperature. Wiens displacement law determines the most likely frequency of the radiation. Thermal radiation is one of the mechanisms of heat transfer. Thermal radiation is the emission of electromagnetic waves from all matter that has a greater than absolute zero. It represents a conversion of energy into electromagnetic energy. Thermal energy consists of the energy of random movements of atoms. All matter with a temperature by definition is composed of particles which have kinetic energy, and these atoms and molecules are composed of charged particles, i. e. protons and electrons, and kinetic interactions among matter particles result in charge-acceleration and dipole-oscillation. This results in the generation of coupled electric and magnetic fields, resulting in the emission of photons. Electromagnetic radiation, including light, does not require the presence of matter to propagate, the radiation is not monochromatic, i. e. it does not consist of just a single frequency, but comprises a continuous dispersion of photon energies, its characteristic spectrum. If the radiating body and its surface are in thermodynamic equilibrium, a black body is also a perfect emitter. The radiation of such perfect emitters is called black-body radiation, the ratio of any bodys emission relative to that of a black body is the bodys emissivity, so that a black body has an emissivity of unity. Absorptivity, reflectivity, and emissivity of all bodies are dependent on the wavelength of the radiation, the temperature determines the wavelength distribution of the electromagnetic radiation
16.
Diffuse reflection
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Diffuse reflection is the reflection of light from a surface such that an incident ray is reflected at many angles rather than at just one angle as in the case of specular reflection. An illuminated ideal diffuse reflecting surface will have equal luminance from all directions which lie in the adjacent to the surface. A surface built from a non-absorbing powder such as plaster, or from such as paper, or from a polycrystalline material such as white marble. Many common materials exhibit a mixture of specular and diffuse reflection, the visibility of objects, excluding light-emitting ones, is primarily caused by diffuse reflection of light, it is diffusely-scattered light that forms the image of the object in the observers eye. Diffuse reflection from solids is not due to surface roughness. A flat surface is indeed required to give specular reflection, a piece of highly polished white marble remains white, no amount of polishing will turn it into a mirror. Polishing produces some specular reflection, but the light continues to be diffusely reflected. All these rays walk through the snow crystallytes, which do not absorb light, until they arrive at the surface, the result is that the light that was sent out is returned in all directions, so that snow is white despite being made of transparent material. This mechanism is very general, because almost all materials are made of small things held together. Mineral materials are polycrystalline, one can describe them as made of a 3D mosaic of small. Organic materials are composed of fibers or cells, with their membranes. And each interface, inhomogeneity or imperfection can deviate, reflect or scatter light, virtually all materials can give specular reflection, provided that their surface can be polished to eliminate irregularities comparable with light wavelength. Diffuse reflection from white materials, instead, can be efficient in giving back all the light they receive. Up to this point white objects have been discussed, which do not absorb light, but the above scheme continues to be valid in the case that the material is absorbent. In this case, diffused rays will lose some wavelengths during their walk in the material, diffusion affects the color of objects in a substantial manner because it determines the average path of light in the material, and hence to which extent the various wavelengths are absorbed. Red ink looks black when it stays in its bottle and its vivid color is only perceived when it is placed on a scattering material. This is so because lights path through the fibers is only a fraction of millimeter long. However, light from the bottle has crossed several centimeters of ink and has been heavily absorbed, and, when a colored object has both diffuse and specular reflection, usually only the diffuse component is colored
17.
World Meteorological Organization
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The World Meteorological Organization is an intergovernmental organization with a membership of 191 Member States and Territories. It originated from the International Meteorological Organization, which was founded in 1873 and its current Secretary-General is Petteri Taalas and the President of the World Meteorological Congresss, its supreme body, is David Grimes. The Organization is headquartered in Geneva, Switzerland, the World Meteorological Organization is a specialized agency of the United Nations. WMO has a membership of 191 Member States and Territories as of February 2014, the Convention of the World Meteorological Organization was signed 11 October 1947 and established upon ratification on 23 March 1950. WMO became the agency of the United Nations in 1951 for meteorology, operational hydrology. It originated from the International Meteorological Organization, which was founded in 1873, the WMO hierarchy, The World Meteorological Congress, the supreme body of the Organization, determines policy. Each member state and territory is represented by a Permanent Representative with WMO when Congress meets every four years, Congress elects the President and Vice-Presidents of the Organization and members of the Executive Council, and appoints the Secretary-General. The Executive Council implements Congress decisions, the Executive Council normally hold a session at least once a year. Six Regional Associations are responsible for the coordination of meteorological, hydrological and they meet once every four years, and elect a president and vice-president. The president of regional association is an ex officio member of the Executive Council. Eight Technical Commissions are responsible for studying meteorological and hydrological operational systems, applications and they establish methodology and procedures and make recommendations to Executive Council and the World Meteorological Congress. The Secretariat is headed by the Secretary-General, who is appointed by the World Meteorological Congress for a term with a maximum tenure of 8 years. The Secretary-General appoints all staff, including the Deputy Secretary-General and the Assistant Secretary-General, the Secretariat currently has around 300 staff. Weather, climate and the water cycle shape almost every aspect of our lives and these powerful natural forces do not recognize national borders, thus global and regional cooperation is essential. Even the accuracy of a weather forecast relies on observations from far beyond national borders. These warnings help to save lives and to protect property. They contribute to economic planning and decision-making, and help minimize the harm that weather, climate, the first step in producing weather forecasts is to gather non-stop observations of the environment from around the world. WMO develops the standards for designing these and other observing instruments and for ensuring that the collected data are quality controlled
18.
Sunshine duration
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It is a general indicator of cloudiness of a location, and thus differs from insolation, which measures the total energy delivered by sunlight over a given period. Sunshine duration is usually expressed in hours per year, or in hours per day, the first measure indicates the general sunniness of a location compared with other places, while the latter allows for comparison of sunshine in various seasons in the same location. Another often-used measure is percentage ratio of recorded bright sunshine duration, an important use of sunshine duration data is to characterize the climate of sites, especially of health resorts. This also takes account the psychological effect of strong solar light on human well-being. It is often used to promote tourist destinations, if the Sun were to be above the horizon 50% of the time for a standard year consisting of 8,760 hours, apparent maximal daytime duration would be 4,380 hours for any point on Earth. However, there are physical and astronomical effects that change that picture, namely, atmospheric refraction allows the Sun to be still visible even when it physically sets below the horizon. For that reason, average daytime is longest in polar areas, places on the Arctic Circle have the longest total annual daytime,4,647 hours, while the North Pole receives 4,575. Because of elliptic nature of the Earths orbit, the Southern Hemisphere is not symmetrical, the Equator has a total daytime of 4,422 hours per year. Given the theoretical maximum of daytime duration for a given location, bright sunshine hours represent the total hours when the sunlight is stronger than a specified threshold, as opposed to just visible hours. Visible sunshine, for example, occurs around sunrise and sunset, measurement is performed by instruments called sunshine recorders. For the specific purpose of sunshine duration recording, Campbell–Stokes recorders are used, when the intensity exceeds a pre-determined threshold, the tape burns. The total length of the trace is proportional to the number of bright hours. Another type of recorder is the Jordan sunshine recorder, newer, electronic recorders have more stable sensitivity than that of the paper tape. In 2003, the duration was finally defined as the period during which direct solar irradiance exceeds a threshold value of 120 W/m². The sky is clear in these regions, and fair weather is virtually perpetual, the descending branch of the Hadley cell and the long-term lack of atmospheric disturbances helps to explain the seemingly endless supply of sunny, cloud-free days in the deserts. Low clouding conditions are associated with rainfall shortage, as seen in these dry regions. In the belt encompassing northern Chad and the Tibesti Mountains, northern Sudan, southern Libya, some places in the interior of the Arabian Peninsula receive 3, 600–3,800 hours of bright sunshine annually. The largest sun-baked region in the world is North Africa, the sunniest month in the world is December in Eastern Antarctica, with almost 23 hours of bright sun daily
19.
Vitamin D3
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Cholecalciferol, also known as vitamin D3 and colecalciferol, is a type of vitamin D found in food and used as a dietary supplement. As a supplement it is used to treat and prevent vitamin D deficiency including rickets and it is also used for familial hypophosphatemia, hypoparathyroidism that is causing low blood calcium, and Fanconi syndrome. Excessive doses can result in vomiting, constipation, weakness, normal doses are safe in pregnancy. It may not be effective in people with kidney disease. After being converted into 1, 25-dihydroxyvitamin D, it works by increasing the uptake of calcium by the intestines, food in which it is found include some fish, cheese, and eggs. Cholecalciferol was first described in 1936 and it is on the World Health Organizations List of Essential Medicines, the most effective and safe medicines needed in a health system. Cholecalciferol is available as a medication and over the counter. The wholesale cost in the world is about 2.14 USD per 30 ml bottle. In the United States treatment costs less than 25 USD per month, certain foods such as milk have cholecalciferol added to them in some countries. One gram is 40,000,000 IU, equivalently 1 IU is 0.025 µg, recommendations vary depending on the country, In the US,15 µg/d for all individuals between the ages of 1 and 70 years old, inclusive. For all individuals older than 70 years,20 µg/d is recommended, in the EU,20 µg/d In France,25 µg/d Many question whether the current recommended intake is sufficient to meet physiological needs. Individuals without regular sun exposure, the obese, and darker skinned individuals all have lower blood levels, patients with severe vitamin D deficiency will require treatment with a loading dose, its magnitude can be calculated based on the actual serum 25-hydroxy-vitamin D level and body weight. Also, there is a therapy for rickets utilizing a single dose, called stoss therapy in Europe, taking from 300,000 IU to 500,000 IU, in a single dose, or in two to four divided doses. There are conflicting reports concerning the absorption of cholecalciferol versus ergocalciferol, with studies suggesting less efficacy of D2. At present, D2 and D3 doses are considered interchangeable. A meta-analysis of 2007 concluded that intake of 1000 to 2000 IU per day of vitamin D3 could reduce the incidence of colorectal cancer with minimal risk. In humans, with 400 IU daily, there was no effect of cholecalciferol supplements on the risk of colorectal cancer, supplements are not recommended for prevention of cancer as any effects of cholecalciferol are very small. It is a secosteroid, that is, a molecule with one ring open
20.
Mutagen
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In genetics, a mutagen is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level. As many mutations can cause cancer, mutagens are also likely to be carcinogens. Some chemicals only become mutagenic through cellular processes, not all mutations are caused by mutagens, so-called spontaneous mutations occur due to spontaneous hydrolysis, errors in DNA replication, repair and recombination. The first mutagens to be identified were carcinogens, substances that were shown to be linked to cancer. Tumors were described more than 2,000 years before the discovery of chromosomes and DNA, in 500 B. C. the Greek physician Hippocrates named tumors resembling a crab karkinos, meaning crab. In 1775, Sir Percivall Pott wrote a paper on the incidence of scrotal cancer in chimney sweeps. In 1915, Yamagawa and Ichikawa showed that repeated application of coal tar to rabbits ears produced malignant cancer, subsequently, in the 1930s the carcinogen component in coal tar was identified as a polyaromatic hydrocarbon, benzopyrene. Polyaromatic hydrocarbons are also present in soot, which was suggested to be an agent of cancer over 150 years earlier. His collaborator Edgar Altenburg also demonstrated the effect of UV radiation in 1928. Muller went on to use x-rays to create Drosophila mutants that he used in his studies of genetics and he also found that X-rays not only mutate genes in fruit flies but also have effects on the genetic makeup of humans. Similar work by Lewis Stadler also showed the effect of X-ray on barley in 1928. The effect of sunlight had previously noted in the nineteenth century where rural outdoor workers and sailors were found to be more prone to skin cancer. Chemical mutagens were not demonstrated to cause mutation until the 1940s, early studies by Ames showed around 90% of known carcinogens can be identified in Ames test as mutagenic, and ~80% of the mutagens identified through Ames test may also be carcinogens. Mutagens are not necessarily carcinogens, and vice versa, sodium azide for example may be mutagenic, but it has not been shown to be carcinogenic. Mutagens can cause changes to the DNA and are therefore genotoxic and they can affect the transcription and replication of the DNA, which in severe cases can lead to cell death. The mutagen produces mutations in the DNA, and deleterious mutation can result in aberrant, impaired or loss of function for a particular gene, mutagens may therefore be also carcinogens. Different mutagens act on the DNA differently, powerful mutagens may result in chromosomal instability, causing chromosomal breakages and rearrangement of the chromosomes such as translocation, deletion, and inversion. Some mutagens can cause aneuploidy and change the number of chromosomes in the cell, in Ames test, where the varying concentrations of the chemical are used in the test, the dose response curve obtained is nearly always linear, suggesting that there is no threshold for mutagenesis
21.
Photosynthesis
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Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms activities. In most cases, oxygen is released as a waste product. Most plants, most algae, and cyanobacteria perform photosynthesis, such organisms are called photoautotrophs, in plants, these proteins are held inside organelles called chloroplasts, which are most abundant in leaf cells, while in bacteria they are embedded in the plasma membrane. In these light-dependent reactions, some energy is used to strip electrons from suitable substances, such as water, in the Calvin cycle, atmospheric carbon dioxide is incorporated into already existing organic carbon compounds, such as ribulose bisphosphate. Using the ATP and NADPH produced by the light-dependent reactions, the compounds are then reduced and removed to form further carbohydrates. Cyanobacteria appeared later, the oxygen they produced contributed directly to the oxygenation of the Earth. Today, the rate of energy capture by photosynthesis globally is approximately 130 terawatts. Photosynthetic organisms also convert around 100–115 thousand million tonnes of carbon into biomass per year. Photosynthetic organisms are photoautotrophs, which means that they are able to synthesize food directly from carbon dioxide, however, not all organisms that use light as a source of energy carry out photosynthesis, photoheterotrophs use organic compounds, rather than carbon dioxide, as a source of carbon. In plants, algae, and cyanobacteria, photosynthesis releases oxygen and this is called oxygenic photosynthesis and is by far the most common type of photosynthesis used by living organisms. Although there are differences between oxygenic photosynthesis in plants, algae, and cyanobacteria, the overall process is quite similar in these organisms. There are also varieties of anoxygenic photosynthesis, used mostly by certain types of bacteria. Carbon dioxide is converted into sugars in a process called carbon fixation, photosynthesis provides the energy in the form of free electrons that are used to split carbon from carbon dioxide that is then used to fix that carbon once again as carbohydrate. Carbon fixation is a redox reaction, so photosynthesis supplies the energy that drives both process. In the first stage, light-dependent reactions or light reactions capture the energy of light and use it to make the energy-storage molecules ATP, during the second stage, the light-independent reactions use these products to capture and reduce carbon dioxide. Most organisms that utilize oxygenic photosynthesis use visible light for the light-dependent reactions, some organisms employ even more radical variants of photosynthesis. Some archea use a method that employs a pigment similar to those used for vision in animals. The bacteriorhodopsin changes its configuration in response to sunlight, acting as a proton pump and this produces a proton gradient more directly, which is then converted to chemical energy
22.
Autotroph
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An autotroph or producer, is an organism that produces complex organic compounds from simple substances present in its surroundings, generally using energy from light or inorganic chemical reactions. They are the producers in a chain, such as plants on land or contrast to heterotrophs as consumers of autotrophs). They do not need a source of energy or organic carbon. Autotrophs can reduce carbon dioxide to organic compounds for biosynthesis. Most autotrophs use water as the agent, but some can use other hydrogen compounds such as hydrogen sulfide. Some autotrophs, like plants and algae, are phototrophs. Autotrophs can be photoautotrophs or chemoautotrophs, lithotrophs use inorganic compounds, such as hydrogen sulfide, elemental sulfur, ammonium and ferrous iron, as reducing agents for biosynthesis and chemical energy storage. Photoautotrophs and lithoautotrophs use a portion of the ATP produced during photosynthesis or the oxidation of inorganic compounds to reduce NADP+ to NADPH to form organic compounds, the greek term autotroph was coined by the german botanist Albert Bernhard Frank in 1892. Some organisms rely on organic compounds as a source of carbon, such organisms are not defined as autotrophic, but rather as heterotrophic. Evidence suggests that some fungi may also obtain energy from radiation, such radiotrophic fungi were found growing inside a reactor of the Chernobyl nuclear power plant. Autotrophs are fundamental to the chains of all ecosystems in the world. They take energy from the environment in the form of sunlight or inorganic chemicals and this mechanism is called primary production. Other organisms, called heterotrophs, take in autotrophs as food to carry out functions necessary for their life. Thus, heterotrophs — all animals, almost all fungi, as well as most bacteria and protozoa — depend on autotrophs, or primary producers, for the energy, heterotrophs obtain energy by breaking down organic molecules obtained in food. Carnivorous organisms rely on autotrophs indirectly, as the nutrients obtained from their heterotroph prey come from autotrophs they have consumed, most ecosystems are supported by the autotrophic primary production of plants that capture photons initially released by the sun. Plants convert and store the energy of the photon into the bonds of simple sugars during photosynthesis. These plant sugars are polymerized for storage as long-chain carbohydrates, including other sugars, starch, when autotrophs are eaten by heterotrophs, i. e. consumers such as animals, the carbohydrates, fats, and proteins contained in them become energy sources for the heterotrophs. Proteins can be made using nitrates, sulfates, and phosphates in the soil, autotroph Chemoautotroph Lithotroph Photoautotroph Heterotroph Chemoheterotroph Lithotroph Photoheterotroph Organotroph Primary nutritional groups Heterotrophic nutrition
23.
Radiant energy
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In physics, and in particular as measured by radiometry, radiant energy is the energy of electromagnetic and gravitational radiation. As energy, its SI unit is the joule, the quantity of radiant energy may be calculated by integrating radiant flux with respect to time. The symbol Qe is often used throughout literature to denote radiant energy, in branches of physics other than radiometry, electromagnetic energy is referred to using E or W. The term is used particularly when electromagnetic radiation is emitted by a source into the surrounding environment and this radiation may be visible or invisible to the human eye. The term radiant energy is most commonly used in the fields of radiometry, solar energy, heating and lighting, in modern applications involving transmission of power from one location to another, radiant energy is sometimes used to refer to the electromagnetic waves themselves, rather than their energy. In the past, the term electro-radiant energy has also been used, the term radiant energy also applies to gravitational radiation. For example, the first gravitational waves ever observed were produced by a black hole collision that emitted about 5. 3×1047 joules of gravitational-wave energy. Because electromagnetic radiation can be conceptualized as a stream of photons, alternatively, EM radiation can be viewed as an electromagnetic wave, which carries energy in its oscillating electric and magnetic fields. These two views are completely equivalent and are reconciled to one another in quantum field theory, EM radiation can have various frequencies. The bands of frequency present in a given EM signal may be defined, as is seen in atomic spectra, or may be broad. In the photon picture, the energy carried by each photon is proportional to its frequency, in the wave picture, the energy of a monochromatic wave is proportional to its intensity. This implies that if two EM waves have the intensity, but different frequencies, the one with the higher frequency contains fewer photons. When EM waves are absorbed by an object, the energy of the waves is converted to heat and this is a very familiar effect, since sunlight warms surfaces that it irradiates. Often this phenomenon is associated particularly with infrared radiation, but any kind of radiation will warm an object that absorbs it. EM waves can also be reflected or scattered, in case their energy is redirected or redistributed as well. Radiant energy is one of the mechanisms by which energy can enter or leave an open system, such a system can be man-made, such as a solar energy collector, or natural, such as the Earths atmosphere. In geophysics, most atmospheric gases, including the greenhouse gases, allow the Suns short-wavelength radiant energy to pass through to the Earths surface, heating the ground and oceans. The absorbed solar energy is partly re-emitted as longer wavelength radiation, radiant energy is produced in the sun as a result of nuclear fusion
24.
Sunshine recorder
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A sunshine recorder is a device that records the amount of sunshine at a given location. The results provide information about the weather and climate as well as the temperature of a geographical area and this information is useful in meteorology, science, agriculture, tourism, and other fields. It has also called a heliograph. There are two types of sunshine recorders. One type uses the sun itself as a time-scale for the sunshine readings, the other type uses some form of clock for the time scale. Older recorders required a human observer to interpret the results, recorded results might differ among observers, modern sunshine recorders use electronics and computers for precise data that do not depend on a human interpreter. Newer recorders can also measure the global and diffuse radiation, global dimming Pictures of the papers produced by a Sunlight Recorder Blake-Larsen Sunlight Recorder Komoka Sunrecorder Current Images
25.
Pyranometer
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The name pyranometer stems from the Greek words πῦρ, meaning fire, and ἄνω, meaning above, sky. A typical pyranometer does not require any power to operate, the solar radiation spectrum that reach earth surface extends its wavelength approximately from 300 to 2,800 nm. Depending on the type of pyranometer used, irradiance measurements with different degrees of spectral sensitivity will be obtained, to make a measurement of irradiance, it is required by definition that the response to “beam” radiation varies with the cosine of the angle of incidence. This ensures a full response when the solar radiation hits the sensor perpendicularly, zero response when the sun is at the horizon and it follows that a pyranometer should have a so-called “directional response” or “cosine response” close to the ideal cosine characteristic. The light sensitivity, known as response, depends on the type of pyranometer. The figure to the shows the spectral responses of the three types of pyranometer in relation to the Solar Radiation Spectrum. The Solar Radiation Spectrum represents the spectrum of sunlight that reaches the Earth’s surface at sea level, the latitude and altitude influence this spectrum. The spectrum is influenced also by aerosol and pollution, a thermopile pyranometer is a sensor based on thermopiles designed to measure the broadband of the solar radiation flux density from a 180° field of view angle. In all thermopile technology, irradiation is proportional to the difference between the temperature of the sun exposed area and the temperature of the shadow area. In order to attain the proper directional and spectral characteristics, a thermopile pyranometer is constructed with the main components. It absorbs all radiation, has a flat spectrum covering the 300 to 50,000 nanometer range. It limits the spectral response from 300 to 2,800 nanometers and it also shields the thermopile sensor from convection. In the modern thermopile pyranometers the active junctions of the thermopile are located beneath the coating surface and are heated by the radiation absorbed from the black coating. The passive junctions of the thermopile are fully protected from radiation and in thermal contact with the pyranometer housing. This prevents any alteration from yellowing or decay when measuring the temperature in the shade, the thermopile generates a small voltage in proportion to the temperature difference between the black coating surface and the instrument housing. This is of the order of 10 µ • VW/m2, typically, on a sunny day the output is around 10 mV. Each pyranometer has a sensitivity, unless otherwise equipped with a board for signal calibration. Thermopile pyranometers are used in meteorology, climatology, climate change research, building engineering physics
26.
Pyrheliometer
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A pyrheliometer is an instrument for measurement of direct beam solar irradiance. Sunlight enters the instrument through a window and is directed onto a thermopile which converts heat to a signal that can be recorded. The signal voltage is converted via a formula to measure watts per square metre and it is used with a solar tracking system to keep the instrument aimed at the sun. A pyrheliometer is often used in the setup with a pyranometer. Pyrheliometer measurement specifications are subject to International Organization for Standardization and World Meteorological Organization standards, Comparisons between pyrheliometers for intercalibration are carried out regularly to measure the amount of solar energy received. The aim of the International Pyrheliometer Comparisons, which place every 5 years at the World Radiation Centre in Davos, is to ensure the world-wide transfer of the World Radiometric Reference. During this event, all bring their instruments, solar-tracking. Actinometer Active cavity radiometer Pyrometer Solar constant Bolometer
27.
Orbital eccentricity
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The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is an orbit, values between 0 and 1 form an elliptical orbit,1 is a parabolic escape orbit. The term derives its name from the parameters of conic sections and it is normally used for the isolated two-body problem, but extensions exist for objects following a rosette orbit through the galaxy. In a two-body problem with inverse-square-law force, every orbit is a Kepler orbit, the eccentricity of this Kepler orbit is a non-negative number that defines its shape. The limit case between an ellipse and a hyperbola, when e equals 1, is parabola, radial trajectories are classified as elliptic, parabolic, or hyperbolic based on the energy of the orbit, not the eccentricity. Radial orbits have zero angular momentum and hence eccentricity equal to one, keeping the energy constant and reducing the angular momentum, elliptic, parabolic, and hyperbolic orbits each tend to the corresponding type of radial trajectory while e tends to 1. For a repulsive force only the trajectory, including the radial version, is applicable. For elliptical orbits, a simple proof shows that arcsin yields the projection angle of a circle to an ellipse of eccentricity e. For example, to view the eccentricity of the planet Mercury, next, tilt any circular object by that angle and the apparent ellipse projected to your eye will be of that same eccentricity. From Medieval Latin eccentricus, derived from Greek ἔκκεντρος ekkentros out of the center, from ἐκ- ek-, eccentric first appeared in English in 1551, with the definition a circle in which the earth, sun. Five years later, in 1556, a form of the word was added. The eccentricity of an orbit can be calculated from the state vectors as the magnitude of the eccentricity vector, e = | e | where. For elliptical orbits it can also be calculated from the periapsis and apoapsis since rp = a and ra = a, where a is the semimajor axis. E = r a − r p r a + r p =1 −2 r a r p +1 where, rp is the radius at periapsis. For Earths annual orbit path, ra/rp ratio = longest_radius / shortest_radius ≈1.034 relative to center point of path, the eccentricity of the Earths orbit is currently about 0.0167, the Earths orbit is nearly circular. Venus and Neptune have even lower eccentricity, over hundreds of thousands of years, the eccentricity of the Earths orbit varies from nearly 0.0034 to almost 0.058 as a result of gravitational attractions among the planets. The table lists the values for all planets and dwarf planets, Mercury has the greatest orbital eccentricity of any planet in the Solar System. Such eccentricity is sufficient for Mercury to receive twice as much solar irradiation at perihelion compared to aphelion, before its demotion from planet status in 2006, Pluto was considered to be the planet with the most eccentric orbit
28.
Elliptic orbit
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In astrodynamics or celestial mechanics an elliptic orbit is a Kepler orbit with the eccentricity less than 1, this includes the special case of a circular orbit, with eccentricity equal to zero. In a stricter sense, it is a Kepler orbit with the eccentricity greater than 0, in a wider sense it is a Kepler orbit with negative energy. This includes the radial elliptic orbit, with eccentricity equal to 1, in a gravitational two-body problem with negative energy both bodies follow similar elliptic orbits with the same orbital period around their common barycenter. Also the relative position of one body with respect to the other follows an elliptic orbit, examples of elliptic orbits include, Hohmann transfer orbit, Molniya orbit and tundra orbit. A is the length of the semi-major axis, the velocity equation for a hyperbolic trajectory has either +1 a, or it is the same with the convention that in that case a is negative. Conclusions, For a given semi-major axis the orbital energy is independent of the eccentricity. ν is the true anomaly. The angular momentum is related to the cross product of position and velocity. Here ϕ is defined as the angle which differs by 90 degrees from this and this set of six variables, together with time, are called the orbital state vectors. Given the masses of the two bodies they determine the full orbit, the two most general cases with these 6 degrees of freedom are the elliptic and the hyperbolic orbit. Special cases with fewer degrees of freedom are the circular and parabolic orbit, another set of six parameters that are commonly used are the orbital elements. In the Solar System, planets, asteroids, most comets, the following chart of the perihelion and aphelion of the planets, dwarf planets and Halleys Comet demonstrates the variation of the eccentricity of their elliptical orbits. For similar distances from the sun, wider bars denote greater eccentricity, note the almost-zero eccentricity of Earth and Venus compared to the enormous eccentricity of Halleys Comet and Eris. A radial trajectory can be a line segment, which is a degenerate ellipse with semi-minor axis =0. Although the eccentricity is 1, this is not a parabolic orbit, most properties and formulas of elliptic orbits apply. However, the orbit cannot be closed and it is an open orbit corresponding to the part of the degenerate ellipse from the moment the bodies touch each other and move away from each other until they touch each other again. In the case of point masses one full orbit is possible, the velocities at the start and end are infinite in opposite directions and the potential energy is equal to minus infinity. The radial elliptic trajectory is the solution of a problem with at some instant zero speed
29.
Extinction (astronomy)
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In astronomy, extinction is the absorption and scattering of electromagnetic radiation by dust and gas between an emitting astronomical object and the observer. Interstellar extinction was first documented as such in 1930 by Robert Julius Trumpler. For stars that lie near the plane of the Milky Way and are within a few parsecs of the Earth. For Earth-bound observers, extinction arises both from the medium and the Earths atmosphere, it may also arise from circumstellar dust around an observed object. The strong atmospheric extinction in some wavelength regions requires the use of space-based observatories, since blue light is much more strongly attenuated than red light, extinction causes objects to appear redder than expected, a phenomenon referred to as interstellar reddening. Reddening occurs due to the light scattering off dust and other matter in the interstellar medium, interstellar reddening is a different phenomenon from redshift, which is the proportional frequency shifts of spectra without distortion. Reddening preferentially removes shorter wavelength photons from a spectrum while leaving behind the longer wavelength photons. In any photometric system interstellar reddening can be described by color excess, an objects intrinsic color index is the theoretical color index which it would have if unaffected by extinction. This is similar to the effect seen when dust particles in the atmosphere of Earth contribute to red sunsets, broadly speaking, interstellar extinction is strongest at short wavelengths, generally observed by using techniques from spectroscopy. Extinction results in a change in the shape of an observed spectrum, superimposed on this general shape are absorption features that have a variety of origins and can give clues as to the chemical composition of the interstellar material, e. g. dust grains. Known absorption features include the 2175 Å bump, the diffuse interstellar bands, the 3.1 μm water ice feature, and the 10 and 18 μm silicate features. In the solar neighborhood, the rate of extinction in the Johnson-Cousins V-band is usually taken to be 0. 7-1.0 mag/kpc−simply an average due to the clumpiness of interstellar dust. In general, however, this means that a star will have its brightness reduced by about a factor of 2 in the V-band for every kiloparsec it is away from us. The amount of extinction can be higher than this in specific directions. For example, some regions of the Galactic Center have more than 30 magnitudes of extinction in the optical, extending the extinction law into the mid-infrared wavelength range is difficult due to the lack of suitable targets and various contributions by absorption features. R is defined to be A/E, and measures the total, A, to selective, E = A-A, a and A are the total extinction at the B and V filter bands. Another measure used in the literature is the absolute extinction A/A at wavelength λ, R is known to be correlated with the average size of the dust grains causing the extinction. For our own galaxy, the Milky Way, the value for R is 3.1
30.
Apsis
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An apsis is an extreme point in an objects orbit. The word comes via Latin from Greek and is cognate with apse, for elliptic orbits about a larger body, there are two apsides, named with the prefixes peri- and ap-, or apo- added to a reference to the thing being orbited. For a body orbiting the Sun, the point of least distance is the perihelion, the terms become periastron and apastron when discussing orbits around other stars. For any satellite of Earth including the Moon the point of least distance is the perigee, for objects in Lunar orbit, the point of least distance is the pericynthion and the greatest distance the apocynthion. For any orbits around a center of mass, there are the terms pericenter and apocenter, periapsis and apoapsis are equivalent alternatives. A straight line connecting the pericenter and apocenter is the line of apsides and this is the major axis of the ellipse, its greatest diameter. For a two-body system the center of mass of the lies on this line at one of the two foci of the ellipse. When one body is larger than the other it may be taken to be at this focus. Historically, in systems, apsides were measured from the center of the Earth. In orbital mechanics, the apsis technically refers to the distance measured between the centers of mass of the central and orbiting body. However, in the case of spacecraft, the family of terms are used to refer to the orbital altitude of the spacecraft from the surface of the central body. The arithmetic mean of the two limiting distances is the length of the axis a. The geometric mean of the two distances is the length of the semi-minor axis b, the geometric mean of the two limiting speeds is −2 ε = μ a which is the speed of a body in a circular orbit whose radius is a. The words pericenter and apocenter are often seen, although periapsis/apoapsis are preferred in technical usage, various related terms are used for other celestial objects. The -gee, -helion and -astron and -galacticon forms are used in the astronomical literature when referring to the Earth, Sun, stars. The suffix -jove is occasionally used for Jupiter, while -saturnium has very rarely used in the last 50 years for Saturn. The -gee form is used as a generic closest approach to planet term instead of specifically applying to the Earth. During the Apollo program, the terms pericynthion and apocynthion were used when referring to the Moon, regarding black holes, the term peri/apomelasma was used by physicist Geoffrey A. Landis in 1998 before peri/aponigricon appeared in the scientific literature in 2002
31.
Lux
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The lux is the SI unit of illuminance and luminous emittance, measuring luminous flux per unit area. It is equal to one lumen per square metre, in photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. In English, lux is used as both the singular and plural form, illuminance is a measure of how much luminous flux is spread over a given area. One can think of flux as a measure of the total amount of visible light present. A given amount of light will illuminate a surface more dimly if it is spread over a larger area, however, the same 1000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux. Achieving an illuminance of 500 lux might be possible in a kitchen with a single fluorescent light fixture with an output of 12000 lumens. To light a factory floor with dozens of times the area of the kitchen would require dozens of such fixtures, thus, lighting a larger area to the same level of lux requires a greater number of lumens. As with other SI units, SI prefixes can be used, for instance, a star of apparent magnitude 0 provides 2.08 microlux at the earths surface. A barely perceptible magnitude 6 star provides 8 nanolux, the unobscured sun provides an illumination of up to 100 kilolux on the Earths surface, the exact value depending on time of year and atmospheric conditions. This direct normal illuminance is related to the solar illuminance constant Esc, the illumination provided on a surface by a point source equals the number of lux just described times the cosine of the angle between a ray coming from the source and a normal to the surface. The number of lux falling on the surface equals this cosine times a number that characterizes the source from the point of view in question and it differs from the luminance, which does depend on the angular distribution of the emission. A perfectly white surface with one lux falling on it will emit one lux, like all photometric units, the lux has a corresponding radiometric unit. The weighting factor is known as the luminosity function, the lux is one lumen per square metre, and the corresponding radiometric unit, which measures irradiance, is the watt per square metre. The peak of the luminosity function is at 555 nm, the eyes image-forming visual system is sensitive to light of this wavelength than any other. Other wavelengths of visible light produce fewer lux per watt-per-meter-squared, the luminosity function falls to zero for wavelengths outside the visible spectrum. For a light source with mixed wavelengths, the number of lumens per watt can be calculated by means of the luminosity function and this means that white light sources produce far fewer lumens per watt than the theoretical maximum of 683.002 lm/W. The ratio between the number of lumens per watt and the theoretical maximum is expressed as a percentage known as the luminous efficiency. For example, an incandescent light bulb has a luminous efficiency of only about 2%
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Air mass (astronomy)
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In astronomy, air mass is the optical path length through Earth’s atmosphere for light from a celestial source. As it passes through the atmosphere, light is attenuated by scattering and absorption, the atmosphere through which it passes. Consequently, celestial bodies at the horizon appear less bright than when at the zenith, the attenuation, known as atmospheric extinction, is described quantitatively by the Beer–Lambert–Bouguer law. “Air mass” normally indicates relative air mass, the path length relative to that at the zenith at sea level so, by definition, Air mass increases as the angle between the source and the zenith increases, reaching a value of approximately 38 at the horizon. The region above Earth’s atmosphere, where there is no attenuation of solar radiation, is considered to have “air mass zero”. Tables of air mass have been published by authors, including Bemporad, Allen. The angle of a body with the zenith is the zenith angle. A body’s angular position can also be given in terms of altitude, the angle above the horizon, the altitude h. Atmospheric refraction causes light to follow a circular path that is slightly longer than the geometric path. Most air mass formulas are based on the apparent zenith angle, when the zenith angle is small to moderate, a good approximation is given by assuming a homogeneous plane-parallel atmosphere. The air mass X then is simply the secant of the angle z, X = sec z. At a zenith angle of 60°, the air mass is approximately 2, the Earth is not flat, however, and, depending on accuracy requirements, this formula is usable for zenith angles up to about 60° to 75°. At greater zenith angles, the accuracy degrades rapidly, with X = sec z becoming infinite at the horizon, the horizon air mass in the more-realistic spherical atmosphere is usually less than 40. Many formulas have been developed to fit tabular values of air mass, one by Young and Irvine included a simple corrective term, X = sec z t and this gives usable results up to approximately 80°, but the accuracy degrades rapidly at greater zenith angles. The calculated air mass reaches a maximum of 11.13 at 86. 6°, becomes zero at 88°, the plot of this formula on the accompanying graph includes a correction for atmospheric refraction so that the calculated air mass is for apparent rather than true zenith angle. Hardie introduced a polynomial in sec z −1, X = sec z −0.0018167 −0.0028752 −0.00080833 which gives usable results for zenith angles of up to perhaps 85°. As with the formula, the calculated air mass reaches a maximum. Rozenberg suggested X = −1, which gives reasonable results for zenith angles
33.
Astronomical unit
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The astronomical unit is a unit of length, roughly the distance from Earth to the Sun. However, that varies as Earth orbits the Sun, from a maximum to a minimum. Originally conceived as the average of Earths aphelion and perihelion, it is now defined as exactly 149597870700 metres, the astronomical unit is used primarily as a convenient yardstick for measuring distances within the Solar System or around other stars. However, it is also a component in the definition of another unit of astronomical length. A variety of symbols and abbreviations have been in use for the astronomical unit. In a 1976 resolution, the International Astronomical Union used the symbol A for the astronomical unit, in 2006, the International Bureau of Weights and Measures recommended ua as the symbol for the unit. In 2012, the IAU, noting that various symbols are presently in use for the astronomical unit, in the 2014 revision of the SI Brochure, the BIPM used the unit symbol au. In ISO 80000-3, the symbol of the unit is ua. Earths orbit around the Sun is an ellipse, the semi-major axis of this ellipse is defined to be half of the straight line segment that joins the aphelion and perihelion. The centre of the sun lies on this line segment. In addition, it mapped out exactly the largest straight-line distance that Earth traverses over the course of a year, knowing Earths shift and a stars shift enabled the stars distance to be calculated. But all measurements are subject to some degree of error or uncertainty, improvements in precision have always been a key to improving astronomical understanding. Improving measurements were continually checked and cross-checked by means of our understanding of the laws of celestial mechanics, the expected positions and distances of objects at an established time are calculated from these laws, and assembled into a collection of data called an ephemeris. NASAs Jet Propulsion Laboratory provides one of several ephemeris computation services, in 1976, in order to establish a yet more precise measure for the astronomical unit, the IAU formally adopted a new definition. Equivalently, by definition, one AU is the radius of an unperturbed circular Newtonian orbit about the sun of a particle having infinitesimal mass. As with all measurements, these rely on measuring the time taken for photons to be reflected from an object. However, for precision the calculations require adjustment for such as the motions of the probe. In addition, the measurement of the time itself must be translated to a scale that accounts for relativistic time dilation
34.
Zenith
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The zenith is an imaginary point directly above a particular location, on the imaginary celestial sphere. Above means in the direction opposite to the apparent gravitational force at that location. The opposite direction, i. e. the direction in which gravity pulls, is toward the nadir, the zenith is the highest point on the celestial sphere. It was reduced to samt and miswritten as senit/cenit, as the m was misread as an ni, through the Old French cenith, zenith first appeared in the 17th century. The term zenith is sometimes used to refer to the highest point, way or level reached by a celestial body during its apparent orbit around a given point of observation. This sense of the word is used to describe the location of the Sun, but to an astronomer the sun does not have its own zenith. In a scientific context, the zenith is the direction of reference for measuring the zenith angle, in astronomy, the altitude in the horizontal coordinate system and the zenith angle are complementary angles, with the horizon perpendicular to the zenith. The astronomical meridian is also determined by the zenith, and is defined as a circle on the sphere that passes through the zenith, nadir. A zenith telescope is a type of telescope designed to point straight up at or near the zenith, the NASA Orbital Debris Observatory and the Large Zenith Telescope are both zenith telescopes since the use of liquid mirrors meant these telescopes could only point straight up. Azimuth Geodesy History of geodesy Keyhole problem Midheaven Subsolar point Vertical deflection Horizontal coordinate system Glickman, Todd S. Glossary of meteorology
35.
Luminous efficacy
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Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power, measured in lumens per watt in SI, depending on context, the power can be either the radiant flux of the sources output, or it can be the total power consumed by the source. Which sense of the term is intended must usually be inferred from the context, the former sense is sometimes called luminous efficacy of radiation, and the latter luminous efficacy of a source or overall luminous efficacy. The luminous efficacy of a source is the product of how well it converts energy to electromagnetic radiation, luminous efficacy can be normalized by the maximum possible luminous efficacy to a dimensionless quantity called luminous efficiency. Wavelengths of light outside of the spectrum are not useful for illumination because they cannot be seen by the human eye. Furthermore, the eye responds more to some wavelengths of light than others and this response of the eye is represented by the luminosity function. This is a function which represents the response of a typical eye under bright conditions. One can also define a curve for dim conditions. When neither is specified, photopic conditions are generally assumed, luminous efficacy of radiation measures the fraction of electromagnetic power which is useful for lighting. It is obtained by dividing the luminous flux by the radiant flux, light with wavelengths outside the visible spectrum reduces luminous efficacy, because it contributes to the radiant flux while the luminous flux of such light is zero. Wavelengths near the peak of the eyes response contribute more strongly than those near the edges, photopic luminous efficacy of radiation has a maximum possible value of 683 lm/W, for the case of monochromatic light at a wavelength of 555 nm. Scotopic luminous efficacy of radiation reaches a maximum of 1700 lm/W for monochromatic light at a wavelength of 507 nm, artificial light sources are usually evaluated in terms of luminous efficacy of the source, also sometimes called wall-plug efficacy. This is the ratio between the luminous flux emitted by a device and the total amount of input power it consumes. The luminous efficacy of the source is a measure of the efficiency of the device with the output adjusted to account for the response curve. When expressed in dimensionless form, this value may be called luminous efficiency of a source, luminous efficacy of radiation is a property of the radiation emitted by a source. Luminous efficacy of a source is a property of the source as a whole, the following table lists luminous efficacy of a source and efficiency for various light sources. Note that all lamps requiring electrical/electronic ballast are unless noted listed without losses for that, even at this high temperature, a lot of the radiation is either infrared or ultraviolet, and the theoretical luminous is 95 lumens per watt. No substance is solid and usable as a light bulb filament at temperatures close to this
36.
Lumen (unit)
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The lumen is the SI derived unit of luminous flux, a measure of the total quantity of visible light emitted by a source. Lumens are related to lux in that one lux is one lumen per square meter, the lumen is defined in relation to the candela as 1 lm =1 cd ⋅ sr. A full sphere has an angle of 4π steradians, so a light source that uniformly radiates one candela in all directions has a total luminous flux of 1 cd × 4π sr = 4π cd⋅sr ≈12.57 lumens. If a light source emits one candela of luminous intensity uniformly across a solid angle of one steradian, alternatively, an isotropic one-candela light-source emits a total luminous flux of exactly 4π lumens. If the source were partly covered by an ideal absorbing hemisphere, the luminous intensity would still be one candela in those directions that are not obscured. The lumen can be thought of casually as a measure of the amount of visible light in some defined beam or angle. The number of candelas or lumens from a source also depends on its spectrum, the difference between the units lumen and lux is that the lux takes into account the area over which the luminous flux is spread. A flux of 1000 lumens, concentrated into an area of one square metre, the same 1000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux. Mathematically,1 lx =1 lm/m2, a source radiating a power of one watt of light in the color for which the eye is most efficient has luminous flux of 683 lumens. So a lumen represents at least 1/683 watts of light power. Lamps used for lighting are commonly labelled with their output in lumens. A23 W spiral compact fluorescent lamp emits about 1, 400–1,600 lm, many compact fluorescent lamps and other alternative light sources are labelled as being equivalent to an incandescent bulb with a specific wattage. Below is a table that shows typical luminous flux for common incandescent bulbs, on September 1,2010, European Union legislation came into force mandating that lighting equipment must be labelled primarily in terms of luminous flux, instead of electric power. This change is a result of the EUs Eco-design Directive for Energy-using Products, for example, according to the European Union standard, an energy-efficient bulb that claims to be the equivalent of a 60 W tungsten bulb must have a minimum light output of 700–750 lm. The light output of projectors is typically measured in lumens, a standardized procedure for testing projectors has been established by the American National Standards Institute, which involves averaging together several measurements taken at different positions. For marketing purposes, the flux of projectors that have been tested according to this procedure may be quoted in ANSI lumens. ANSI lumen measurements are in more accurate than the other measurement techniques used in the projector industry. This allows projectors to be easily compared on the basis of their brightness specifications
37.
Lighting
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Lighting or illumination is the deliberate use of light to achieve a practical or aesthetic effect. Lighting includes the use of artificial light sources like lamps and light fixtures, as well as natural illumination by capturing daylight. Daylighting is sometimes used as the source of light during daytime in buildings. This can save energy in place of using lighting, which represents a major component of energy consumption in buildings. Proper lighting can enhance performance, improve the appearance of an area. Indoor lighting is accomplished using light fixtures, and is a key part of interior design. Lighting can also be a component of landscape projects. With the discovery of fire, the earliest form of lighting used to illuminate an area were campfires or torches. As early as 400,000 BCE, fire was kindled in the caves of Peking Man, prehistoric people used primitive oil lamps to illuminate surroundings. These lamps were made from naturally occurring materials such as rocks, shells, horns and stones, were filled with grease, lamps typically used animal or vegetable fats as fuel. Hundreds of these lamps have been found in the Lascaux caves in modern-day France, oily animals were also used as lamps after being threaded with a wick. Fireflies have been used as lighting sources, candles and glass and pottery lamps were also invented. Chandeliers were a form of light fixture. A major reduction in the cost of lighting occurred with the discovery of whale oil, in 1849, Dr. Abraham Gesner, a Canadian geologist, devised a method where kerosene could be distilled from petroleum. Earlier coal-gas methods had been used for lighting since the 1820s, gesners kerosene was cheap, easy to produce, could be burned in existing lamps, and did not produce an offensive odor as did most whale oil. It could be stored indefinitely unlike whale oil, which would eventually spoil, the American petroleum boom began in the 1850s. By the end of the decade there were 30 kerosene plants operating in the United States, the cheaper, more efficient fuel began to drive whale oil out of the market. John D. Rockefeller was most responsible for the success of kerosene
38.
Illuminance
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In photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, similarly, luminous emittance is the luminous flux per unit area emitted from a surface. Luminous emittance is also known as luminous exitance, in SI derived units these are measured in lux or lumens per square metre. In the CGS system, the unit of illuminance is the phot, the foot-candle is a non-metric unit of illuminance that is used in photography. Illuminance was formerly often called brightness, but this leads to confusion with other uses of the word, brightness should never be used for quantitative description, but only for nonquantitative references to physiological sensations and perceptions of light. In astronomy, the illuminance stars cast on the Earths atmosphere is used as a measure of their brightness, the usual units are apparent magnitudes in the visible band. V-magnitudes can be converted to lux using the formula E v =10 /2.5, where Ev is the illuminance in lux, the reverse conversion is M v = −14.18 −2.5 log . Autodesk Design Academy - Measuring Light Levels
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South Pole
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The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earths axis of rotation intersects its surface. It is the southernmost point on the surface of the Earth, situated on the continent of Antarctica, it is the site of the United States Amundsen–Scott South Pole Station, which was established in 1956 and has been permanently staffed since that year. The Geographic South Pole should not be confused with the South Magnetic Pole, the South Pole is at the center of the Southern Hemisphere. For most purposes, the Geographic South Pole is defined as the point of the two points where the Earths axis of rotation intersects its surface. However, the Earths axis of rotation is actually subject to very small wobbles, the geographic coordinates of the South Pole are usually given simply as 90°S, since its longitude is geometrically undefined and irrelevant. When a longitude is desired, it may be given as 0°, at the South Pole, all directions face north. For this reason, directions at the Pole are given relative to grid north, along tight latitude circles, clockwise is east, and counterclockwise is west, opposite to the North Pole. The Geographic South Pole is located on the continent of Antarctica. It sits atop a featureless, barren, windswept and icy plateau at an altitude of 2,835 metres above sea level, and is located about 1,300 km from the nearest open sea at Bay of Whales. The ice is estimated to be about 2,700 metres thick at the Pole, the polar ice sheet is moving at a rate of roughly 10 metres per year in a direction between 37° and 40° west of grid north, down towards the Weddell Sea. Therefore, the position of the station and other artificial features relative to the geographic pole gradually shift over time. The Geographic South Pole is marked by a stake in the ice alongside a small sign, these are repositioned each year in a ceremony on New Years Day to compensate for the movement of the ice. The sign records the respective dates that Roald Amundsen and Robert F. Scott reached the Pole, followed by a quotation from each man. A new marker stake is designed and fabricated each year by staff at the site, the Ceremonial South Pole is an area set aside for photo opportunities at the South Pole Station. It is located around 180 metres from the Geographic South Pole, Amundsens Tent, The tent was erected by the Norwegian expedition led by Roald Amundsen on its arrival on 14 December 1911. It is currently buried beneath the snow and ice in the vicinity of the Pole and it has been designated a Historic Site or Monument, following a proposal by Norway to the Antarctic Treaty Consultative Meeting. In 1820, several expeditions claimed to have been the first to have sighted Antarctica, with the very first being the Russian expedition led by Faddey Bellingshausen and Mikhail Lazarev. The first landing was probably just over a year later when American Captain John Davis, the basic geography of the Antarctic coastline was not understood until the mid-to-late 19th century
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