Artificial sunlight
Encyclopedia
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
where the unique benefits of sunlight are needed, but where sufficient natural sunlight is not available or is not feasible. A light source used to simulate sunlight is a solar simulator
Solar Simulator
A solar simulator is a device that provides illumination approximating natural sunlight. The purpose of the solar simulator is to provide a controllable indoor test facility under laboratory conditions, used for the testing of solar cells, sun screen, plastics, and other materials and...
.
Composition of natural sunlight
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...
striking the Earth's atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
is 100 to 106 nanometer (nm). This can be divided into five regions in increasing order of wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s:
- Ultraviolet C or (UVC) range
- Ultraviolet B or (UVB) range
- Ultraviolet A or (UVA) range
- Visible range or lightLightLight or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
- InfraredInfraredInfrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
range. It is further divided into three types on the basis of wavelength:- Infrared-A
- Infrared-B
- Infrared-C
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.Light therapy
Artificial sunlight is found useful in treating and preventing Seasonal affective disorderSeasonal affective disorder
Seasonal affective disorder , also known as winter depression, winter blues, summer depression, summer blues, or seasonal depression, is a mood disorder in which people who have normal mental health throughout most of the year experience depressive symptoms in the winter or summer, spring or autumn...
(also known as winter depression, which brings about depressive
Depression (mood)
Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behaviour, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, or restless...
symptoms specifically in winter), and Delayed sleep phase syndrome
Delayed sleep phase syndrome
Delayed sleep-phase syndrome , also known as delayed sleep-phase disorder or delayed sleep-phase type , is a circadian rhythm sleep disorder, a chronic disorder of the timing of sleep, peak period of alertness, the core body temperature rhythm, hormonal and other daily rhythms, compared to the...
, in which the circadian (day V/s night)-rhythm
Circadian rhythm
A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...
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
Jet lag
Jet lag, medically referred to as desynchronosis, is a physiological condition which results from alterations to the body's circadian rhythms; it is classified as one of the circadian rhythm sleep disorders...
.
Aquarium lighting
Different coralCoral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
s in a reef aquarium
Reef aquarium
A reef aquarium or reef tank is an marine aquarium that prominently displays live corals and other marine invertebrates as well as fish that play a role in maintaining the coral reef environment...
require different lighting conditions. Most of the corals are symbiotically
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
dependent upon zooxanthellae—a type of algae. It is the zooxanthellae that require light to perform photosynthesis, and they provide the coral polyps 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
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
-controlled that make it possible to simulate daybreak, sunset, and even the various phases of moon
Lunar phase
A lunar phase or phase of the moon is the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun...
. However, this technology is relatively expensive. Also, some animals like the Red-eared slider
Red-eared slider
The red-eared slider is a semiaquatic turtle belonging to the family Emydidae. It is a subspecies of pond slider. It is the most popular pet turtle in the United States and also popular in the rest of the world...
turtle are benefited of having those lights fitted on their aquariums.
Product testing
Testing the efficacy of sunscreenSunscreen
Sunblock is a lotion, spray, gel or other topical product that absorbs or reflects some of the sun's ultraviolet radiation on the skin exposed to sunlight and thus helps protect against sunburn...
s requires the use of solar simulators.
Manufacturers of solar cell
Solar cell
A solar cell is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect....
s must test the overall efficiency of the cells. They require to be tested indoors, which has traditionally been performed using mostly Sulphur plasma lamps or xenon arc lamp
Xenon arc lamp
A xenon arc lamp is a specialized type of gas discharge lamp, an electric light that produces light by passing electricity through ionized xenon gas at high pressure to produce a bright white light that closely mimics natural sunlight...
.
Within the automotive industry, solar simulation tests are used to ensure automotive system reliability and functionality.
Artificial sunlight (solar simulators) are also used for sun light exposure testing and of color fastness and material stability for textile, plastics and paints.