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The Sun may be said to illuminate, which is a measure of the light within a specific sensitivity range. Many animals (including humans) have a sensitivity range of approximately 400–700 nm, [ 43 ] and given optimal conditions the absorption and scattering by Earth's atmosphere produces illumination that approximates an equal-energy illuminant ...
An example of this phenomenon is when clean air scatters blue light more than red light, and so the midday sky appears blue (apart from the area around the Sun which appears white because the light is not scattered as much). The optical window is also referred to as the "visible window" because it overlaps the human visible response spectrum.
Above infrared in frequency comes visible light. The Sun emits its peak power in the visible region, although integrating the entire emission power spectrum through all wavelengths shows that the Sun emits slightly more infrared than visible light. [15] By definition, visible light is the part of the EM spectrum the human eye is the most ...
Extremely hot stars (such as O- and B-type) emit proportionally more UV radiation than the Sun. Sunlight in space at the top of Earth's atmosphere (see solar constant) is composed of about 50% infrared light, 40% visible light, and 10% ultraviolet light, for a total intensity of about 1400 W/m 2 in vacuum.
Red "Very high" A UV index reading of 8 to 10 means very high risk of harm from unprotected sun exposure. Take extra precautions because unprotected skin and eyes will be damaged and can burn quickly. Minimize sun exposure between 10 a.m. and 4 p.m. If outdoors, seek shade and wear sun-protective clothing, a wide-brimmed hat, and UV-blocking ...
A common phenotype of UV coloration is the “bulls-eye” pattern where a flower reflects UV light at the ends of the petals and absorbs UV light in the center. [4] This acts as a guide for pollinators to locate and find pollen. [4] Other flowers add the contrast between their reproductive parts (anthers and pistils) and their petals. [7]
Here, the path of sunlight through the atmosphere is elongated such that much of the blue or green light is scattered away from the line of perceivable visible light. This phenomenon leaves the Sun's rays, and the clouds they illuminate, abundantly orange-to-red in colors, which one sees when looking at a sunset or sunrise.
The Sun closely approximates a black-body radiator. The effective temperature, defined by the total radiative power per square unit, is 5772 K. [12] The color temperature of sunlight above the atmosphere is about 5900 K. [13] The Sun may appear red, orange, yellow, or white from Earth, depending on its position in the sky.