It is about 3.3% higher than average in January and 3.3% lower in July (see below). The total amount of energy received at ground level from the Sun at the zenith depends on the distance to the Sun and thus on the time of year. The atmospheric extinction brings the number of lux down to around 100,000 lux. Where c is the atmospheric extinction and m is the relative optical airmass. The extraterrestrial solar illuminance ( E ext), corrected for the elliptic orbit by using the day number of the year (dn), is given to a good approximation by E e x t = E s c ⋅ ( 1 + 0.033412 ⋅ cos ( 2 π d n − 3 365 ) ), To calculate the amount of sunlight reaching the ground, both the eccentricity of Earth's elliptic orbit and the attenuation by Earth's atmosphere have to be taken into account. Researchers can measure the intensity of sunlight using a sunshine recorder, pyranometer, or pyrheliometer. Solar irradiance is the solar energy available from sunlight. Sunlight is a key factor in photosynthesis, the process used by plants and other autotrophic organisms to convert light energy, normally from the Sun, into chemical energy that can be used to synthesize carbohydrates and fuel the organisms' activities.ĭaylighting is the natural lighting of interior spaces by admitting sunlight. A photon starting at the center of the Sun and changing direction every time it encounters a charged particle would take between 10,000 and 170,000 years to get to the surface. Sunlight takes about 8.3 minutes to reach Earth from the surface of the Sun. The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a requisite for vitamin D 3 synthesis and a mutagen. Sources estimate a global average of between 164 watts to 340 watts per square meter over a 24-hour day this figure is estimated by NASA to be about a quarter of Earth's average total solar irradiance. When blocked by clouds or reflected off other objects, sunlight is diffused. When direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon. Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. Sunrise over the Gulf of Mexico and Florida. Both are filtered through high stratus clouds. Sunrise on the Jersey Shore at Spring Lake, Monmouth County (above), and sunset on the Shore at Sunset Beach, Cape May County (below). Sunlight shining upon two different sides of the U.S.
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