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| | What is sunlight and what does it do? |
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| | Sunlight, in the broad sense, is the total spectrum of the electromagnetic radiation given off by the sun. On earth, sunlight is filtered through the atmosphere, and the solar radiation is obvious as daylight when the sun is above the horizon. The total frequency of the electromagnetic radiation striking the earth's atmosphere can be anywhere between 100 and 1,000,000 nanometers (or 1 mm) depending on, among others, the earth's position and the status of the atmosphere. It can be divided into five regions in increasing order of wavelengths:
Ultraviolet C (or UVC), ranging from 200 to 290 nm appr., Ultraviolet B (or UVB), ranging from 290 to 320 nm appr., Ultraviolet A (or UVA), ranging from 320 to 400 nm appr., Visible range (or light), spanning 400 to 760 nm appr., and Infrared, from 7060 to 1 mm appr.
UVC radiation is potentially harmful, but is mostly blocked by the earth's atmosphere. The shortwave UVB radiation has, by itself, no temperature but converts to warmth through absorption and consequently into the long-wave, heat-producing UVA radiation. This heat is the main cause of sunburn in humans and animals. Conventional interior sun block systems, such as vertical, horizontal and roll blinds, absorb incoming sunlight radiation. Due to the change of its wavelength, the energy-rich radiation is then transformed into heat.
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