Artificial sunlight
5548064
220132517
2008-06-18T12:47:43Z
Alan Liefting
36352
-cats
[[Image:HappyLite.jpg|thumb|The HappyLite, a type of [[light therapy]].]]
'''Artificial sunlight''' is the use of a [[List of light sources| light source]] to simulate [[sunlight]] where the unique benefits of sunlight are needed, but where sufficient natural sunlight is not available or is not feasible. The concept has various applications including [[greenhouse]] lighting, [[Sun tanning|tanning of skin]], [[light therapy]] and even in [[refrigerators]] to preserve the freshness of vegetables. A light source used to simulate the sunlight would be known as a '''solar simulator.'''
== Composition of natural sunlight ==
{{Further|[[Sunlight#Composition of sunlight| composition of sunlight]]}}
[[Image:Solar Spectrum.png|thumb|250px|Solar irradiance spectrum above atmosphere and at surface]]The spectrum of [[electromagnetic radiation]] striking the [[Earth's atmosphere]] is 100 to 10<sup>6</sup> [[nanometer| nanometer (nm)]]. This can be divided into five regions in increasing order of [[wavelength]]s:<ref>{{cite web|last=Naylor|first=Mark|coauthors=Kevin C. Farmer|title='"Sun damage and prevention"|work=Electronic Textbook of Dermatology|publisher=The Internet Dermatology Society|date=[[1995]]|url= http://www.telemedicine.org/sundam/sundam2.4.1.html|accessdate=2008-06-02}}</ref>
* '''[[Ultraviolet C]]''' or (UVC) range
* '''[[Ultraviolet B]]''' or (UVB) range
* '''[[Ultraviolet A]]''' or (UVA) range
* '''[[Visible light|Visible range]]''' or '''[[light]]'''
* '''[[Infrared]]''' range. It is further divided into three types on the basis of wavelength:
** Infrared-A
** Infrared-B
** Infrared-C
== Light sources ==
* '''[[Incandescent bulb]]s''' These bulbs contain a metallic [[Electrical filament| filament]] usually made up of [[tungsten]] that heats up when electricity passes through it, and emits light when sufficiently high temperature is reached. These bulbs tend to heat up the surroundings.
* '''[[Fluorescent lamp]]s''' are tubes filled with low density [[mercury (element)|mercury]], [[argon]] or [[krypton]]. These lamps basically emit ultraviolet light, which is converted to visible light when these rays strike coated [[phosphor]] (a material that shows a sustained delayed glow after being excited by high energy particles , like [[electrons]] or [[photons]] or "packets" of light (ultraviolet radiation in this case)). The ultraviolet light is produced when the high energy (fast) electrons that are produced in the tube hit the electrons of the gas and "excite" them to higher energy level. This electrons immediately come back to their [[ground state]] (the original lowest energy level at which an electron can stay). This is known as [[fluorescence]]. These sources have greater energy [[efficiency]], and are mainly available in two types— ''warm white bulbs'', which emit light more in the red range (longer wavelength), and ''cold white bulbs'', which emit more of blue light.
* '''[[High-intensity discharge lamp]]s (HID)''' contain tungsten [[electrode]]s and emit light by producing an electric arc through a housed gas and [[plasma (physics)| plasma state]] of a salt loosely, gas in which outer shell electrons have left the individual atoms (ionized gas).
* '''[[LED]] bulbs''' These bulbs use multiple [[Light Emitting Diode]]s to create a large amount of light.
{{Expand-section| more examples of light sources|date=June 2008}}
== Applications ==
[[Image:Artificialsunlight-plants.jpg|thumb|Artificial sunlight lamps are used to provide additional light for plants.]]
=== Horticulture ===
{{Main|Horticulture}}
Horticulture is the art and science of the cultivation of [[plants]]. Plants require sunlight for performing [[photosynthesis]], which results in production of [[glucose]] and other complex [[carbohydrates]]. These nutrients, when stored, provide bulk to [[fruit]]s and [[vegetable]]s. So, upon this [[Wiktionary:premise|premise]], that proper provision of light energy will promote photosynthesis and add to the bulk of the produce, artificial lighting is used in horticulture.<ref name="ge">{{cite web| title=Section on "Light" in hydroponics from growingedge.com|url=http://www.growingedge.com/basics/tutorial/05_lighting.html |accessdate = 2008-06-01}}</ref>
=== Tanning ===
{{Main|Tanning bed}}
Tanning beds emit [[ultraviolet radiation]] using several fluorescent lamps that have phosphor blends designed to emit UV in a spectrum that is somewhat similar to the sun. This creates an artificial environment which creates an [[Sun tanning|cosmetic tan]] on the user.
=== Illumination ===
{{Main|Full-spectrum light}}
It has been claimed that artificial light sources that provide the light of the closest possible spectrum as provided by the Sun have beneficial effects on health and productivity. This technology is known as [[Full-spectrum light| full-spectrum lighting]].<ref>{{cite web |url=http://www.lrc.rpi.edu/programs/nlpip/lightingAnswers/fullSpectrum/abstract.asp |title=''Full-Spectrum Light Sources'' in '''National Lighting Product Information Program''' |accessdate=2008-06-05 |publisher=Rensselaer Polytechnic Institute's ''Lighting Research Center'' |date=2005-03 }}</ref>
=== Light therapy ===
{{Main|Light therapy}}
Artificial sunlight is found useful in treating and preventing [[Seasonal affective disorder]] (also known as ''winter depression'', which brings about [[Depression (mood)| depressive]] symptoms specifically in winter),<ref>{{cite web|url=http://www.sciencenews.org/view/feature/id/7375/title/Light_Impacts|title=Light Impacts|publisher=Science News|accessdate=2008-06-05}}</ref> and [[Delayed sleep phase syndrome]], in which the [[Circadian rhythm| circadian (day V/s night)-rhythm]] is disturbed, and the individual tends to fall asleep ''at the same time'' much after midnight.
Artificial sunlight may also be useful in prevention, or minimizing the severity of [[jet lag]].<ref>{{cite web|url=http://www.news.com.au/story/0,23599,18463197-36335,00.html|title=Kiss jet lag goodbye|publisher=www.news.com.au|accessdate=2008-06-05}}</ref> Although, UV light is used in treatment of [[psoriasis]] and [[eczema]] (as [[PUVA| PUVA therapy]]), and in treatment of [[acne]], (in which case it is also accompanied by application of red light), it is not the entire spectrum of visible light that is employed.
=== Refrigerators ===
{{Main|Refrigerator}}
It has been claimed{{Weasel-inline}} that providing light of a certain spectrum that would promote photosynthesis in stored vegetables and fruits helps in preserving their freshness and [[Nutrient| nutritive value]]. On this basis [[Daewoo#Corporations| Daewoo Electronics]] had got the technology patented.<ref>{{cite web |url=http://www.wipo.int/pctdb/en/wo.jsp?WO=2008004743&IA=WO2008004743&DISPLAY=DESC |title=''REFRIGERATOR CAPABLE OF PROMOTING PHOTOSYNTHESIS OF VEGETABLES AND CONTROL METHOD''—Daewoo Electronics Corporation's patent application for the Refrigerator photosynthesis technology |accessdate=2008-06-05 |publisher=World Intellectual Property Organization |date=2008-01-10 }}</ref> This technology has been utilized in refrigerators manufactured by [[Samsung Electronics]],<ref>{{cite web |url=http://www.samsung.com/in/news/newsRead.do?news_group=productnews&news_type=consumerproduct&news_ctgry=refrigerator&news_seq=7527 |title=Samsung press release for launch of 'Freshtech' refrigerator series in India|accessdate=2008-06-05 |publisher=Samsung Electronics |date=2008-04-11 }}</ref> and [[LG Electronics]].<ref>{{cite web |url=http://uk.lge.com/about/press_release/detail/PRE%7CMENU_5484_8.jhtml |title=''LG Press release of February, 2007 for launch of new products |accessdate=2008-06-05 |publisher= |date=2007-02 }}</ref>
=== Photobiology ===
{{Main|Photobiology}}
[[Photobiology]] is the biological study of the interactions of light with living organisms. This also includes testing the efficacy of [[sunscreen]]s. It requires the use of solar simulators.<ref>{{cite web |url=http://www.photoemission.com/Products/SolarSimulationSystems/SolarSimulationSystems.html |title=Solar simulation systems |accessdate=2008-06-05 |publisher=Photo Emission Tech |date= }}</ref>
=== Testing of solar cells ===
{{Main|Solar Cells}}
A [[solar cell]] is a device that converts the [[Ray (optics)#Interaction with surfaces|incident]] light ray into electrical energy. Usually, as the name suggests, it uses the Sun as the light source. However, to maintain the overall efficiency of these cells, they require to be tested indoors, which has traditionally been performed using the [[xenon arc lamp]].<ref>{{Citation|first=Bisaillon|last=J.C.|first2=J.R.|last2=Cummings|first3=J.S.|last3=Culik|first4=J.D.|last4=Lesko|first5= P.E.|last5=Sims|first6=J.A.|last6=Rand|contribution=Non-traditional light sources for solar cell and module testing|contribution-url =http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=&arnumber=916178&isnumber=19792|title=Photovoltaic Specialists Conference, 2000. Conference Record of the Twenty-Eighth IEEE|year=2000|pages=1498-1501|publisher=IEEE|url=http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=&arnumber=916178&isnumber=19792| doi=10.1109/PVSC.2000.916178|accessdate= 2008-06-05}}</ref>
=== Aquarium lighting ===
Different [[coral]]s in a [[reef aquarium]] require different lighting conditions. Most of the corals are [[Symbiosis| symbiotically]] dependent upon [[zooxanthellae]]—a type of [[Alga| algae]]. It is the latter that require light to perform photosynthesis and provide the latter with [[simple carbohydrates]]. In addition to the above techniques of lighting, a new technique employs [[Light emitting diode| light emitting diodes (LEDs)]]. The advantage of this technology is that the various parameters of lighting such as [[Color theory#Warm vs. cool colors| warmth and coolness of color]] are [[microprocessor]]-controlled that make it possible to simulate daybreak, sunset, and even the various [[Lunar phase| phases of moon]]. However, this technology is relatively expensive.
{{Further|[[Aquarium lighting#Reef| aquarium lighting]], [[Reef aquarium#Lighting| reef lighting]]| aquarium lighting, in general and lighting of reef aquarium, in particular}}
=== Other uses ===
Artificial sunlight (solar simulators) are also used for sun light exposure testing and of ''color fastness'' and ''material stability'' for textile, plastics and paints.<ref>{{cite web |url=http://www.photoemission.com/Products/SolarSimulationSystems/SolarSimulationSystems.html |title=Solar simulation systems |accessdate=2008-06-05 |publisher=Photo Emission Tech |date= }}</ref>
{{Expand-section| more examples of applications|date=June 2008}}
==Negative effects==
[[Tanning bed]]s are known to cause [[skin cancer]], due to the fact that they emit no less [[ultraviolet|UV rays]] than the sun.<ref name="IOL">{{cite web|url=http://www.iol.co.za/index.php?set_id=14&click_id=117&art_id=qw1109653025248N632|title=IOL: Artificial sunlight a big no-no, study finds}}</ref>
==References==
{{reflist|2}}
==External links==
*[http://www.growingedge.com/basics/tutorial/05_lighting.html The Growing Edge - Light]
*[http://www.vidyya.com/vol5/v5i318_3.htm Vitamin D deficiency -- An emerging heath crisis?]
*[http://www.earthsky.org/radioshows/50054/artificial-light-plant-growth Do plants grow well under artificial light?]
{{Template:Artificial light sources}}
[[Category:Lighting]]