Sunlight

Sunlight is the primary source of Earth's light and heat. It 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.

Composition and power

Sunlight is a form of electromagnetic radiation with wavelengths of visible light that range from about 400 nm (violet) to about 700 nm (red). This light is also accompanied by ultraviolet and infrared radiation. The solar constant is the amount of power that the Sun deposits per unit area that is directly exposed to sunlight. The solar constant is equal to approximately 1,368 W/m² (watts per square meter) at a distance of one astronomical unit (AU) from the Sun.

Effects on life

Sunlight has a profound influence on the biosphere and the Earth's climate. It provides the energy that drives photosynthesis, a process that plants and other organisms use to convert carbon dioxide and water into glucose and oxygen. Sunlight also influences the behavior and reproductive cycles of many different life forms.

Health effects

Exposure to sunlight has both positive and negative health effects. The positive effects of sunlight include stimulating the production of vitamin D in the skin and improving mood. However, excessive exposure to sunlight can lead to negative health effects such as sunburn, skin cancer, and damage to the eyes.

Cultural aspects

Throughout history, sunlight has been a symbol in many cultures, representing aspects such as divinity, power, good health, and happiness. Many religions and mythologies see the sun as a god or other powerful entity.

See also

• Daylight
• Sun
• Solar radiation
• Vitamin D

Sunlight Resources
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