Artificial sunlight

Artificial sunlight is the use of a 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, 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

url= http://www.telemedicine.org/sundam/sundam2.4.1.html|accessdate=2008-06-02]
* Ultraviolet C or (UVC) range
* Ultraviolet B or (UVB) range
* Ultraviolet A or (UVA) range
* 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 bulbs These bulbs contain a metallic 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 lamps are tubes filled with low density 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 lamps (HID) contain tungsten electrodes and emit light by producing an electric arc through a housed gas and 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 Diodes to create a large amount of light.

Applications

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 fruits and vegetables. So, upon this , that proper provision of light energy will promote photosynthesis and add to the bulk of the produce, artificial lighting is used in horticulture.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]

Tanning

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 cosmetic tan on the user.

Illumination

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 lighting. [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 ]

Light therapy

Artificial sunlight is found useful in treating and preventing Seasonal affective disorder (also known as "winter depression", which brings about depressive symptoms specifically in winter), [cite web|url=http://www.sciencenews.org/view/feature/id/7375/title/Light_Impacts|title=Light Impacts|publisher=Science News|accessdate=2008-06-05] and Delayed sleep phase syndrome, in which the 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. [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] Although, UV light is used in treatment of psoriasis and eczema (as 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

It has been claimedWeasel-inline that providing light of a certain spectrum that would promote photosynthesis in stored vegetables and fruits helps in preserving their freshness and nutritive value. On this basis Daewoo Electronics had got the technology patented. [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 ] This technology has been utilized in refrigerators manufactured by Samsung Electronics, [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 ] and LG Electronics. [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 ]

Photobiology

Photobiology is the biological study of the interactions of light with living organisms. This also includes testing the efficacy of sunscreens. It requires the use of solar simulators. [cite web |url=http://www.photoemission.com/Products/SolarSimulationSystems/SolarSimulationSystems.html |title=Solar simulation systems |accessdate=2008-06-05 |publisher=Photo Emission Tech |date= ]

Testing of solar cells

A solar cell is a device that converts the 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. [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]

Aquarium lighting

Different corals in a reef aquarium require different lighting conditions. Most of the corals are symbiotically dependent upon zooxanthellae—a type of 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 diodes (LEDs). The advantage of this technology is that the various parameters of lighting such as warmth and coolness of color are microprocessor-controlled that make it possible to simulate daybreak, sunset, and even the various phases of moon. However, this technology is relatively expensive.

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. [cite web |url=http://www.photoemission.com/Products/SolarSimulationSystems/SolarSimulationSystems.html |title=Solar simulation systems |accessdate=2008-06-05 |publisher=Photo Emission Tech |date= ]

Negative effects

Tanning beds are known to cause skin cancer, due to the fact that they emit no less UV rays than the sun.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]

References

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?]