Artificial sunlight
Artificial sunlight is the use of a light source to simulate sunlight where the unique characteristics of sunlight are needed, but where sufficient natural sunlight is unavailable or infeasible. A device used to simulate sunlight is a solar simulator. Composition of natural sunlight. The spectrum of electromagnetic radiation striking the Earth's atmosphere is 100 to 1,000,000 nanometers (nm). This can be divided into five regions in increasing order of wavelengths: Applications. 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 disorder (also known as "winter depression", which brings about depressive symptoms specifically in winter), and Delayed sleep phase syndrome, in which the circadian (day V/s night)-rhythm is disturbed, and the individual tends to fall asleep much later than they would desire. Artificial sunlight may also be useful in prevention, or minimizing the severity of jet lag. 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 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-controlled that make it possible to simulate daybreak, sunset, and even the various phases of moon. However, this technology is relatively expensive. Also, some animals like the Red-eared slider turtle benefit from having those lights fitted  on their aquariums. Product testing. Testing the efficacy of sunscreens requires the use of solar simulators. Manufacturers of solar cells 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. 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.