This video gives a brief overview of solar radiation received on Earth. The transfer of energy from the sun to Earth across nearly empty space happens primarily by radiation. Radiation occurs without the involvement of a physical substance as the medium. The sun emits many forms of electromagnetic radiation in varying quantities.
A perfect radiating body emits energy in all possible wavelengths, but the wave energies are not emitted equally in all wavelengths; a spectrum shows a maximum in energy at a particular wavelength depending upon the temperature of the radiating body. As the temperature increases, the maximum radiation occurs at shorter and shorter wavelengths. The hotter the radiating body, the shorter the wavelength of maximum radiation. For example, a very hot metal rod will emit visible radiation and produce a white glow. On cooling, it will emit more of its energy in longer wavelengths and will glow a reddish color. Eventually no light will be given off, but if you place your hand near the rod, the infrared radiation will be detectable as heat.
The sun's maximum energy output is in shortwave energy, known as visible light.
According to the UCAR COMET Program, about 43% of radiant energy from the sun is in the visible part of the spectrum. That is the total amount of the sun's energy integrated over wavelengths between about 400-700nm. Roughly 49% of solar radiation is infrared between 700nm-1mm; about 7% is from ultra-violet between 100-400mm; less than 1% of solar radiation is emitted as x-rays, gamma rays and radio waves.
Science On a Sphere
