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Sunlight shining through clouds, giving rise to crepuscular rays

Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is filtered through Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon. When the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. When it is blocked by the clouds or reflects off other objects, it is experienced as diffused light. The World Meteorological Organization uses the term "sunshine duration" to mean the cumulative time during which an area receives direct irradiance from the Sun of at least 120 watts per square meter.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a principal source of vitamin D3 and a mutagen.


Sunlight sections
Intro   Summary    Composition and power    Calculation   Solar constant  Total (TSI) and spectral solar irradiance (SSI) upon Earth  Intensity in the Solar System   Surface illumination   Variations in solar irradiance  Life on Earth  Cultural aspects  Effects on human health  See also  References  Further reading  External links  

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Solar::sunlight    Author::solar    Title::journal    Earth::spectrum    Light::surface    Earth's::energy

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Sunlight shining through clouds, giving rise to crepuscular rays

Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is filtered through Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon. When the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. When it is blocked by the clouds or reflects off other objects, it is experienced as diffused light. The World Meteorological Organization uses the term "sunshine duration" to mean the cumulative time during which an area receives direct irradiance from the Sun of at least 120 watts per square meter.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a principal source of vitamin D3 and a mutagen.


Sunlight sections
Intro   Summary    Composition and power    Calculation   Solar constant  Total (TSI) and spectral solar irradiance (SSI) upon Earth  Intensity in the Solar System   Surface illumination   Variations in solar irradiance  Life on Earth  Cultural aspects  Effects on human health  See also  References  Further reading  External links  

PREVIOUS: IntroNEXT: Summary
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