This article is about light emitted by the Sun. For other uses, see Sunlight (disambiguation)."Sunshine" redirects here. For other uses, see Sunshine (disambiguation).For natural lighting of interior spaces by admitting sunlight, see Daylighting. For solar energy available from sunlight, see Insolation.
Sunlight shining through clouds, giving rise to crepuscular rays.Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun, particularly infrared, visible, and ultraviolet light. 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 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 of 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.[1]
Sunlight may be recorded using a sunshine recorder, pyranometer or pyrheliometer. Sunlight takes about 8.3 minutes to reach the Earth.
On average, it takes light thousands of years to leave the sun's interior and then leave its surface. The light that shines down on us today was created between 10,000 and 170,000 years ago.[2]
Direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux. Bright sunlight provides illuminance of approximately 100,000 lux or lumens per square meter at the Earth's surface.
Sunlight is a key factor in photosynthesis, a process vital for life on Earth.