Sunlight shining through clouds in Dunstanburgh, England. A cloud is a visible mass of droplets or frozen crystals floating in the atmosphere above the surface of the Earth or another Planetary body Dunstanburgh Castle lies on a spectacular headland on the coast of Northumberland in northern England, between the villages of Craster and Embleton England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland

Sunlight, in the broad sense, is the total spectrum of the electromagnetic radiation given off by the Sun. Spectroscopy was originally the study of the interaction between Radiation and Matter as a function of Wavelength (λ Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. The Sun (Sol is the Star at the center of the Solar System. On Earth, sunlight is filtered through the atmosphere, and the solar radiation is obvious as daylight when the Sun is above the horizon. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 An optical filter is a device which selectively transmits light having certain properties (often a particular range of Wavelengths that is range of Colours Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Daylight or the light of day is the combination of all direct and indirect Sunlight outdoors during the daytime (and perhaps Twilight) The horizon ( Ancient Greek ὁ ὁρίζων, /ho horídzôn/ from ὁρίζειν, "to limit" is the apparent line that separates This is usually during the hours known as day. Near the poles in summer, sunlight also occurs during the hours known as night and in the winter at the poles sunlight may not occur at any time. A geographical pole, or geographic pole, is either of two fixed points on the surface of a spinning body or Planet, at 90 degrees from the Equator, based When the direct radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and heat. Radiant heat directly produced by the radiation of the sun is different from the increase in atmospheric temperature due to the radiative heating of the atmosphere by the sun's radiation. Thermal radiation is Electromagnetic radiation emitted from the surface of an object which is due to the object's Temperature. Sunlight may be recorded using a sunshine recorder. Sunshine Recorders are used to indicate the amount of sunshine at a given location The World Meteorological Organization defines sunshine as direct irradiance from the Sun measured on the ground of at least 120 W·m⁻². The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International

Direct sunlight gives about 93 lumens of illumination per watt of electromagnetic power, including infrared, visible, and ultra-violet. The lumen (symbol lm) is the SI unit of Luminous flux, a measure of the perceived power of Light. The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second. Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays

Sunlight is a key factor in the process of photosynthesis. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy.

Calculation

To calculate the amount of sunlight reaching the ground both the elliptical orbit of the earth and the earth's atmosphere have to be taken into account. The extraterrestrial solar illuminance (E_ext), corrected for the elliptical orbit by using the day number of the year, known as the Julian date (Jd), is: E_ext=E_sc(1 + 0. 034 * cos(2pi(Jd − 2) / 365))

The solar illuminance constant (E_sc), is equal to 128 Klux. The direct normal illuminance, (E_dn), corrected for the attenuating effects of the atmosphere is given by: E_dn=E_ext*e^-cm

Where c is the atmospheric extinction coefficient and m is the relative optical air mass.

Composition of sunlight

Solar irradiance spectrum above atmosphere and at surface

The spectrum of electromagnetic radiation striking the Earth's atmosphere is 100 to 10⁶ nanometer (nm). Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a This can be divided into five regions in increasing order of wavelengths:^[1]

• Ultraviolet C or (UVC) range, which spans a range of 100 to 280 nm. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. The term ultraviolet implies that the radiation is more intense than the visible range of light (and, hence also invisible to the human eye). Owing to absorption by the atmosphere very little reaches the Earth's surface (Lithosphere). The lithosphere (IPA, from the Greek λίθος for "rocky" + σφαίρα for "sphere" is the solid outermost shell of a rocky Planet. This spectrum of radiation has germicidal properties, and is used in germicidal lamps. A germicidal lamp is a special type of lamp which produces Ultraviolet light (UVC
• Ultraviolet B or (UVB) range spans 280 to 315 nm. It is also greatly absorbed by the atmosphere, and along with UVC is responsible for the photochemical reaction leading to the production of the Ozone layer. See also Photochemistry A photochemical reaction is a Chemical reaction which is induced by light. The photochemical mechanisms that give rise to the ozone layer were worked out by the British physicist Sidney Chapman in 1930
• Ultraviolet A or (UVA) spans 315 to 400 nm. It has been traditionally held as less damaging to the DNA, and hence used in tanning and PUVA therapy for psoriasis. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Sun tanning describes a darkening of the skin (especially of fair-skinned individuals in a natural physiological response stimulated by exposure to ultraviolet (UV radiation PUVA is a Psoralen + UVA treatment for Eczema, Psoriasis and Vitiligo, and Mycosis fungoides[http //www Psoriasis (səˈraɪəsɪs ( suh-RI-uh-sus) is a non-contagious disorder which affects the Skin and Joints It commonly causes red scaly
• Visible range or light spans 400 to 700 nm. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 As the name suggests, it is this range that is visible to the naked eye. Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain
• Infrared range that spans 700 nm to 10⁶ nm [1 millimeter (mm)]. Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of The Millimetre ( American spelling: millimeter, symbol mm) is a unit of Length in the Metric system, equal to It is largely responsible for the warmth or heat that the sunlight carries. In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature It is also divided into three types on the basis of wavelength:
  • Infrared-A: 700 nm to 1400 nm
  • Infrared-B: 1400 nm to 3000 nm
  • Infrared-C: 3000 nm to 1 mm.

For more details on ultraviolet, infrared and visible range of radiations, see Ultraviolet, Infrared, Light, . Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700

Life on Earth

The existence of nearly all life on Earth is fueled by light from the sun. Most autotrophs, such as plants, use the energy of sunlight to turn air into simple sugars—a process known as photosynthesis. An autotroph (from the Greek autos = self and trophe = nutrition is an Organism that produces complex Organic compounds from simple Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. These sugars are then used as building blocks and in other synthetic pathways which allow the organism to grow.

Heterotrophs, such as animals, use light from the sun indirectly by consuming the products of autotrophs, either directly or by consuming other heterotrophs. A heterotrophs, or chemoorganotrophy ( Greek heterone = (another and trophe = nutrition is an Organism that requires The sugars and other molecular components produced by the autotrophs are then broken down, releasing stored solar energy, and giving the heterotroph the energy required for survival. This process is known as respiration. Cellular respiration is the set of the metabolic reactions and processes that take place in Organisms cells to convert biochemical energy from

In prehistory, humans began to further extend this process by putting plant and animal materials to other uses. Stone Age Paleolithic See also Paleolithic, Recent African Origin, Early Homo sapiens, Early human migrations "Paleolithic" They used animal skins for warmth, for example, or wooden weapons to hunt. These skills allowed humans to harvest more of the sunlight than was possible through glycolysis alone, and human population began to grow.

During the Neolithic Revolution, the domestication of plants and animals further increased human access to solar energy. The Neolithic Revolution was the first Agricultural revolution &mdashthe transition from hunting and gathering communities and bands to Agriculture and Fields devoted to crops were enriched by inedible plant matter, providing sugars and nutrients for future harvests. A nutrient is food or chemicals that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment Animals which had previously only provided humans with meat and tools once they were killed were now used for labour throughout their lives, fueled by grasses inedible to humans. Poaceae or Gramineae is a family in the Class Liliopsida of the flowering plants.

The more recent discoveries of coal, petroleum and natural gas are modern extensions of this trend. Petroleum ( L petroleum, from Greek πετρέλαιον, lit Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, These fossil fuels are the remnants of ancient plant and animal matter, formed using energy from sunlight and then trapped within the earth for millions of years. Fossil fuels or mineral fuels are fossil source Fuels that is Hydrocarbons found within the top layer of the Earth’s crust. Because the stored energy in these fossil fuels has accumulated over many millions of years, they have allowed modern humans to massively increase the production and consumption of primary energy. Fossil fuels or mineral fuels are fossil source Fuels that is Hydrocarbons found within the top layer of the Earth’s crust. Primary energy is energy that has not been subjected to any conversion or transformation process As the amount of fossil fuel is large but finite, this cannot continue indefinitely, and various theories exist as to what will follow this stage of human civilization (e. g. alternative fuels, Malthusian catastrophe, new urbanism, peak oil). Alternative fuels, also known as non-conventional Fuels are any Materials or substances that can be used as a Fuel, other than conventional fuels A Malthusian catastrophe (or Malthusian check, crisis, dilemma, disaster, trap, controls, or limit) is a return New Urbanism is an American Urban design movement that arose in the early 1980s

Cultural aspects

Many people find direct sunlight to be too bright for comfort, especially when reading from white paper upon which the sun is directly shining. Indeed, looking directly at the sun can cause permanent vision damage. To compensate for the brightness of sunlight, many people wear sunglasses. Sunglasses or sun glasses are a visual aid variously termed Spectacles or Glasses, which feature lenses that are coloured or darkened to prevent strong Cars, many helmets and caps are equipped with visors to block the sun from direct vision when the sun is at a low angle. A helmet is a form of Protective gear worn on the head to protect it from injuries a variation of the hat A cap is a form of Headgear. Caps have crowns that fit closer than Hats and have no brim or only a Visor. A visor is a surface that protects the eyes, such as shading them from the sun or other bright light or protecting them from objects

Prism splitting light

In colder countries many people prefer sunnier days and often avoid the shade. Shade is the blocking of Sunlight (in particular direct sunshine by any object and also the Shadow created by that object In hotter countries the converse is true; during the midday hours many people prefer to stay inside to remain cool. If they do go outside, they seek shade which may be provided by trees, parasols, and so on. "Parasol" redirects here For other uses see Umbrella (disambiguation, Umbrella (song or Parasol (disambiguation

Sunshine is often blocked from entering buildings through the use of window blinds, awnings, shutters or curtains. For other uses see Blinds (disambiguation For the desktop theming software see WindowBlinds. An awning is a secondary covering attached to the exterior wall of a building A window shutter is a solid and stable Window covering usually consisting of a frame of vertical stiles and horizontal rails (top center and bottom A curtain (in the US also known as a drape or drapery) is a piece of Cloth intended to block or obscure Light, or Drafts, or

Sunbathing

Sunbathing is popular for the cosmetic and potential health benefits of a sun tan, although there are also risks of cellular damage to the skin. Sun tanning describes a darkening of the skin (especially of fair-skinned individuals in a natural physiological response stimulated by exposure to ultraviolet (UV radiation Sunbathing is a popular leisure activity in which a person sits or lies in direct sunshine. Leisure or free time, is a period of Time spent out of work and essential domestic Activity. People often sunbathe in comfortable places where there is ample sunlight. Some common places for sunbathing include the beach, open air swimming pools, the park, the garden, and sidewalk cafés. A swimming pool, swimming bath, wading pool, or simply a pool, is an artificially enclosed Body of water intended for Swimming or A park is a protected area of Land and Water, usually in its natural or semi-natural (landscaped state and set aside for some purpose often to do with human A sidewalk cafe (sometimes called a pavement cafe or Patio) is an outdoor part of a Coffeehouse or Cafe. Sunbathers typically wear limited amounts of clothing or some simply go nude. Nudity is the state of wearing no Clothing. The term' "nudity" can also occasionally be used to refer to wearing significantly less clothing than expected

An alternative some use to sunbathing is to use a sunbed that generates ultraviolet light and can be used indoors regardless of outdoor weather conditions and amount of sun light. A tanning bed or sunbed is a device emitting Ultraviolet radiation (typically 95% UVA and 5% UVB +/-3% used to produce a cosmetic tan. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays

For many people with pale or brownish skin, an additional or primary purpose for sunbathing is to darken one's skin color (get a sun tan) as this is considered in some cultures to be beautiful, associated with outdoor activity, vacations or holidays, and health. Human skin color can range from almost black (due to very high concentrations of the dark brown pigment melanin to nearly colorless (appearing reddish white due to the Blood Sun tanning describes a darkening of the skin (especially of fair-skinned individuals in a natural physiological response stimulated by exposure to ultraviolet (UV radiation Lists of holidays The words holiday or vacation have related meanings in different English-speaking countries and continents but will usually refer to one of Lists of holidays The words holiday or vacation have related meanings in different English-speaking countries and continents but will usually refer to one of Indeed, the body produces vitamin D from sunlight (specifically from the UVB band of ultraviolet light), and excessive seclusion from the sun can lead to deficiency. Vitamin D is a group of fat-soluble Prohormones, the two major forms of which are vitamin D2 (or Ergocalciferol) and vitamin D3 (or Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays An additional reason that some people prefer nude sunbathing is that an "all-over" or "even" tan can be obtained. Nudity is the state of wearing no Clothing. The term' "nudity" can also occasionally be used to refer to wearing significantly less clothing than expected

Skin tanning is achieved by an increase in the dark pigment inside skin cells called melanocytes and it is actually an automatic response mechanism of the body to sufficient exposure to ultraviolet radiation from the sun or from artificial sunlamps. Sun tanning describes a darkening of the skin (especially of fair-skinned individuals in a natural physiological response stimulated by exposure to ultraviolet (UV radiation For the drug referred to as "pigment" see Black tar heroin. Melanocytes are cells located in the bottom layer (the Stratum basale) of the skin's epidermis and in the middle layer of the eye (the Uvea) Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays A tanning bed or sunbed is a device emitting Ultraviolet radiation (typically 95% UVA and 5% UVB +/-3% used to produce a cosmetic tan. Thus, the tan gradually disappears with time, when one is no longer exposed to these sources.

Effects on health

While the production of vitamin D is beneficial to health, excessive sunlight exposure has been linked to all types of skin cancer caused by the ultraviolet part of radiation from sunlight or sunlamps. Skin cancer is a Malignant growth on the Skin which can have many causes Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Sunburn can have mild to severe inflammation effects on skin; this can be avoided by using a proper sunscreen cream or lotion or by gradually building up melanocytes with increasing exposure. A sunburn is a burn to living tissue such as Skin produced by overexposure to Ultraviolet (UV radiation commonly from the Sun 's rays Inflammation ( Latin, inflamatio, to set on fire is the complex biological response of vascular tissues to harmful stimuli such as Pathogens Sunscreen (also known as sunblock or suntan lotion) is a Lotion, spray or other Topical product that absorbs or reflects the Sun 's Another detrimental effect of UV exposure is accelerated skin aging (also called skin photodamage), which produces a difficult to treat cosmetic effect. Aesthetics or esthetics ( also spelled æsthetics) is commonly known as the study of sensory or sensori-emotional values sometimes called (Although some people are concerned that ozone depletion is increasing the incidence of such health hazards. Ozone depletion describes two distinct but related observations a slow steady decline of about 4 percent per decade in the total amount of Ozone in Earth's )

A lack of sunlight, on the other hand, is considered one of the primary causes of seasonal affective disorder (SAD), a serious form of the "winter blues". Seasonal affective disorder ( SAD) also known as winter depression, is a Mood disorder in which people who have normal mental health throughout most of the year experience SAD occurrence is more prevalent in locations further from the tropics, and most of the treatments (other than prescription drugs) involve replicating sunlight via sunlamps tuned to specific wavelengths of light or full-spectrum bulbs.

See also

References

1. Hartmann, Thom (1998). Electromagnetic radiation can be classified into ionizing radiation and Non-ionizing radiation, based on whether it is capable of ionizing atoms and breaking In Physics and Optics, the Fraunhofer lines are a set of Spectral lines named for the German physicist Joseph von Fraunhofer ( 1787 The amount of heat energy received at any location on the globe is a direct effect of sun angle of climate, as the angle at which Sunlight strikes the earth A light beam or beam of light is a narrow Projection of Light energy radiating from a source into a Beam. This is a list of sources of Light, including both natural and artificial sources and both processes and devices. Moonlight is the light that comes to Earth from the Moon. This light does not originate from the Moon but is actually reflected Sunlight. Over-illumination is the presence of lighting intensity ( Illuminance) beyond that required for a specified activity The photochemical mechanisms that give rise to the ozone layer were worked out by the British physicist Sidney Chapman in 1930 Ozone depletion describes two distinct but related observations a slow steady decline of about 4 percent per decade in the total amount of Ozone in Earth's Photic sneeze reflex is a genetic Autosomal dominant trait which causes sneezing when exposed suddenly to bright light possibly many times consecutively A season is one of the major divisions of the Year, generally based on yearly periodic changes in Weather. Thom Hartmann (born May 7, 1951) is an American radio host, Author, and liberal Political commentator. The Last Hours of Ancient Sunlight. London: Hodder and Stoughton. ISBN 0-340-82243-0.
2. MF Holick & M Jenkins (2004) UV Advantage, Simon & Schuster.
3. Outlaw, PC (2008). PC Outlaw Management Team. Grand Rapids, Mi. 49418