sunlit adj : lighted by sunlight; "the sunlit slopes of the canyon"; "violet valleys and the sunstruck ridges"- Wallace Stegner [syn: sunstruck]

English

Etymology

sun + lit

Adjective

1. illuminated by sunlight

See also

• candlelit
• moonlit
• starlit

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. This is usually during the hours known as day. Near the poles in summer, sunlight also occurs during the hours known as night and in the winter at the poles sunlight may not occur at any time. When the direct radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and heat. Radiant heat directly produced by the radiation of the sun is different from the increase in atmospheric temperature due to the radiative heating of the atmosphere by the sun's radiation. Sunlight may be recorded using a sunshine recorder. The World Meteorological Organization defines sunshine as direct irradiance from the Sun measured on the ground of at least 120 W·m−2.

Direct sunlight gives about 93 lumens of illumination per watt of electromagnetic power, including infrared, visible, and ultra-violet.

Sunlight is a key factor in the process of photosynthesis.

Calculation

To calculate the amount of sunlight reaching the ground both the elliptical orbit of the earth and the earth's atmosphere have to be taken into account. The extraterrestrial solar illuminance (Eext), corrected for the elliptical orbit by using the day number of the year, known as the Julian date (Jd), is: Eext=Esc(1+0.034 * cos(2pi(Jd-2)/365))

The solar illuminance constant (Esc), is equal to 128 Klux. The direct normal illuminance, (Edn), corrected for the attenuating effects of the atmosphere is given by: Edn=Eext*e-cm

Where c is the atmospheric extinction coefficient and m is the relative optical air mass.

Composition of sunlight

• Earth's atmosphere
• Color temperature
• Crepuscular rays, rays of sunlight that appear to radiate from a single point in the sky.
• Electromagnetic radiation and health
• Fraunhofer line
• Effect of sun angle on climate
• Light beam
• List of light sources
• Moonlight
• Over-illumination
• Ozone layer
• Ozone hole
• Photic sneeze reflex
• Season
• Sunbeam

References

1. Hartmann, Thom (1998). The Last Hours of Ancient Sunlight. London: Hodder and Stoughton. ISBN 0-340-82243-0.
2. MF Holick & M Jenkins (2004) UV Advantage, Simon & Schuster.
3. Outlaw, PC (2008). PC Outlaw Management Team. Grand Rapids, Mi. 49418

ablaze, aglow, alight, bathed with light, bespangled, brightened, candlelit, enlightened, firelit, gaslit, illuminated, in a blaze, irradiate, irradiated, lamplit, lanternlit, lighted, lightened, lit, lit up, luminous, moonlit, spangled, star-spangled, star-studded, starlit, studded, tinseled