Hi Everybody!!

A little treat tonight for lovers of baby birds. We are celebrating the third batch of babies for this year. This little guy is still spotty until his new red feathers fill in. He is on a post in front of the greenhouse plastic, eating seed. He is less than 2 weeks old and learning about the world around him. In your photostudy tonight, You will notice the movement of sunlight. There are other sources of movement: the bird is in constant motion, the sun is moving, the clouds are moving. the greenhouse plastic is moving, the wind is blowing the leaves in the trees and moving the filtered shade. Also, I am moving the camera. You should consider all things when shooting outdoors in Sunlight! Enjoy!

http://en.wikipedia.org/wiki/Sunlight

Sunlight

From Wikipedia, the free encyclopedia

Sunlight is a portion of the electromagnetic radiation given off by the Sun, particularly infrared, visible, and ultraviolet light. On Earth, sunlight is filtered through the Earth's atmosphere, and is obvious as daylight when the Sun is above thehorizon. When the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of brightlight and radiant heat. When it is blocked by the clouds or reflects off other objects, it is experienced as diffused light. TheWorld 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 on the skin is an effective source of vitamin D.

Sunlight shining through clouds, giving rise tocrepuscular rays.

Summary[edit|edit source]

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 energy between 10,000 and 170,000 years to leave the sun's interior and then be emitted from the surface as light.^[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. The total amount of energy received at ground level from the sun at the zenith is 1004 watts per square meter, which is composed of 527 watts of infrared radiation, 445 watts of visible light, and 32 watts of ultraviolet radiation. At the top of the atmosphere sunlight is about 30% more intense, with more than three times the fraction of ultraviolet (UV), with most of the extra UV consisting of biologically-damaging shortwave ultraviolet.^[3]^[4]^[5]

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 fuel the organisms' activities.

Composition and power[edit|edit source]

Solar irradiance spectrum above atmosphere and at surface. Extreme UV and X-rays are produced (at left of wavelength range shown) but comprise very small amounts of the Sun's total output power.

See also: Ultraviolet, Infrared, and Light

The spectrum of the Sun's solar radiation is close to that of a black body with a temperature of about 5,800 K.^[6] The Sun emits EM radiation across most of the electromagnetic spectrum. Although the Sun produces Gamma rays as a result of the nuclear fusion process, these super high energy photons are converted to lower energy photons before they reach the Sun's surface and are emitted out into space. As a result, the Sun does not emit gamma rays. The Sun does, however, emit X-rays, ultraviolet, visible light, infrared, and even radio waves.^[7]

Although the solar corona is a source of extreme ultraviolet and X-ray radiation, these rays make up only a very small amount of the power output of the Sun (see spectrum at right). The spectrum of nearly all solar electromagnetic radiation striking the Earth's atmosphere spans a range of 100 nm to about 1 mm. This band of significant radiation power can be divided into five regions in increasing order of wavelengths:^[8]

Ultraviolet C or (UVC) range, which spans a range of 100 to 280 nm. The term ultraviolet refers to the fact that the radiation is at higher frequency than violet light (and, hence also invisible to the human eye). Owing to absorption by the atmosphere very little reaches the Earth's surface. This spectrum of radiation has germicidal properties, and is used in germicidal lamps.
Ultraviolet B or (UVB) range spans 280 to 315 nm. It is also greatly absorbed by the atmosphere, and along with UVC is responsible for the photochemical reaction leading to the production of the ozone layer. It directly damages DNA and causes sunburn.
Ultraviolet A or (UVA) spans 315 to 400 nm. This band was once held to be less damaging to DNA, and hence is used in cosmetic artificial sun tanning (tanning booths and tanning beds) and PUVA therapy for psoriasis. However, UV A is now known to cause significant damage to DNA via indirect routes (formation of free radicals and reactive oxygen species), and is able to cause cancer.^[9]
Visible range or light spans 380 to 780 nm. As the name suggests, it is this range that is visible to the naked eye. It is also the strongest output range of the sun's total irradiance spectrum.
Infrared range that spans 700 nm to 10⁶ nm (1 mm). It is responsible for an important part of the electromagnetic radiation that reaches the Earth. It is also divided into three types on the basis of wavelength:
- Infrared-A: 700 nm to 1,400 nm
- Infrared-B: 1,400 nm to 3,000 nm
- Infrared-C: 3,000 nm to 1 mm.

Sunlight in space at the top of Earth's atmosphere at a power of 1366 watts/m² is composed (by total energy) of about 50% infrared light, 40% visible light, and 10% ultraviolet light.^[3] At ground level this decreases to about 1120–1000 watts/m², and by energy fractions to 44% visible light, 3% ultraviolet (with the Sun at the zenith, but less at other angles), and the remainder infrared.^[4] Thus, sunlight's composition at ground level, per square meter, with the sun at the zenith, is about 527 watts of infrared radiation, 445 watts of visible light, and 32 watts of ultraviolet radiation.^[5]

Life on Earth[edit|edit source]

The existence of nearly all life on Earth is fueled by light from the sun. Most autotrophs, such as plants, use the energy of sunlight, combined with carbon dioxide and water, to produce simple sugars—a process known as photosynthesis. These sugars are then used as building blocks and in other synthetic pathways which allow the organism to grow.

Heterotrophs, such as animals, use light from the sun indirectly by consuming the products of autotrophs, either by consuming autotrophs, by consuming their products or by consuming other heterotrophs. The sugars and other molecular components produced by the autotrophs are then broken down, releasing stored solar energy, and giving the heterotroph the energy required for survival. This process is known as cellular respiration.

In prehistory, humans began to further extend this process by putting plant and animal materials to other uses. They used animal skins for warmth, for example, or wooden weapons to hunt. These skills allowed humans to harvest more of the sunlight than was possible through glycolysis alone, and human population began to grow.

During the Neolithic Revolution, the domestication of plants and animals further increased human access to solar energy. Fields devoted to crops were enriched by inedible plant matter, providing sugars and nutrients for future harvests. Animals which had previously only provided humans with meat and tools once they were killed were now used for labour throughout their lives, fueled by grasses inedible to humans.

The more recent discoveries of coal, petroleum and natural gas are modern extensions of this trend. These fossil fuels are the remnants of ancient plant and animal matter, formed using energy from sunlight and then trapped within the earth for millions of years. Because the stored energy in these fossil fuels has accumulated over many millions of years, they have allowed modern humans to massively increase the production and consumption of primary energy. As the amount of fossil fuel is large but finite, this cannot continue indefinitely, and various theories exist as to what will follow this stage of human civilization (e.g. alternative fuels, Malthusian catastrophe,new urbanism, peak oil).

Please see above link for complete detailed article.

...this is brendasue signing off from Rainbow Creek. See You next time! If You have not begun to feed the birds, plan to Make August the month You start to Feed the Birds! They are soon to be Migrating for the Fall.