Feb 16, 2009

Radiation characteristics

Electromagnetic radiation is transmitted through a kind of energy. As gravity or a magnet in a vacuum can pendulum swing, the same electromagnetic wave energy having to go through any medium can be in a vacuum delivery. X-ray, ultraviolet, visible light, microwaves, radio waves are a kind of electromagnetic wave. The biggest impact of climate mostly between the ultraviolet to the infrared band, is the strongest band of solar radiation . 

 Any object are emitted radiation will be. Radiation properties of a material if compliance with the basic law of radiation (such as Pu Planck's law (Planck's law), external causes of displacement law (Wien's displacement law), law Quejido (Kirchoff 's law) and so on, referred to as blackbody (blackbody ), are ideal for one's material circumstances. blackbody absorbed all the incident radiation, is neither reflective nor penetrating radiation. blackbody radiation, one of the characteristics are the energy and temperature is proportional to the fourth (this is the law of Pu-Poulenc ). spread to the Earth's solar radiation from sunlight many balls (which are part of the naked eye to see), its temperature is about 5800K; the Earth's radiation balance temperature of 255K. If the sun and the Earth as a blackbody, solar radiation intensity radiation intensity of the Earth about 300,000 times. 

 A blackbody radiation characteristics of the material, if the higher temperature, emitted energy concentrated in the shorter wavelength band; In contrast, low temperature, energy concentrated in the longer wavelength band. This is the external causes of displacement law, which is a maximum energy of electromagnetic waves is inversely proportional to wavelength and temperature. Such as the Sun as a blackbody, the biggest part of the radiation concentrated in the visible light (wavelength of 0.4 ~ 0.7μm). Temperature of the Earth's radiation balance is well below the temperature of the sun, so the energy concentrated in the longer-wavelength infrared band (wavelength around the near 10μm). 

 From Figure 3-2, we can clearly see the sun and earth radiation energy concentrated band, a great difference between each other, overlapping part of small and very small in the energy band. We, therefore, can easily distinguish between the Sun and the Earth's radiation. Solar radiation due to a shorter wavelength, commonly known as short-wave radiation; earth radiation, relatively speaking, a longer wavelength, known as long-wave radiation.

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