Heat Radiation

Thermal radiation is electromagnetic radiation produced by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation. The mechanism is that bodies with a temperature above absolute zero have atoms or molecules with kinetic energies which are changing, and these changes result in charge-acceleration and/or dipole oscillation of the charges that compose the atoms. This motion of charges produces electromagnetic radiation in the usual way. However, the side spectrum of this radiation reflects the wide spectrum of energies and accelerations of the charges in any piece of matter at even a particular temperature.

Examples of thermal radiation include the visible light and infrared light emitted by an incandescent light bulb, the infrared radiation emitted by animals and detectable with an infrared camera, and the cosmic microwave background radiation. Thermal radiation is different from thermal convection and thermal conduction—a person near a raging bonfire feels radiant heating from the fire, even if the surrounding air is very cold.

Heat Radiation

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Heat Radiation

Sunlight is thermal radiation generated by the hot plasma of the Sun. The Earth also radiates thermal radiation, but at a much lower intensity and different spectral distribution (infrared rather than visible) because it is cooler. The Earth’s absorption of solar radiation, followed by its outgoing thermal radiation are the two most important processes that determine the temperature and climate of the World.

Heat Radiation

Heat Radiation

Heat Radiation

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Heat Radiation

Heat Radiation

Heat Radiation

Heat Radiation

Heat Radiation

Heat Radiation

Heat Radiation

Heat Radiation

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Heat Radiation