The heat energy is emitted from a warm element (floor, wall, overhead panel) and warms people and other objects in rooms rather than directly heating the air. It can be generated electrically by infrared lamps, or can be absorbed from sunlight and used to heat water. Radiant energy is used for radiant heating. Radiant energy is produced in the sun as a result of nuclear fusion. The absorbed solar energy is partly re-emitted as longer wavelength radiation (chiefly infrared radiation), some of which is absorbed by the atmospheric greenhouse gases.
In geophysics, most atmospheric gases, including the greenhouse gases, allow the Sun's short-wavelength radiant energy to pass through to the Earth's surface, heating the ground and oceans. Such a system can be man-made, such as a solar energy collector, or natural, such as the Earth's atmosphere. Radiant energy is one of the mechanisms by which energy can enter or leave an open system. EM waves can also be reflected or scattered, in which case their energy is redirected or redistributed as well. Often this phenomenon is associated particularly with infrared radiation, but any kind of electromagnetic radiation will warm an object that absorbs it. This is a very familiar effect, since sunlight warms surfaces that it irradiates. When EM waves are absorbed by an object, the energy of the waves is converted to heat (or converted to electricity in case of a photoelectric material). This implies that if two EM waves have the same intensity, but different frequencies, the one with the higher frequency "contains" fewer photons, since each photon is more energetic. In the wave picture, the energy of a monochromatic wave is proportional to its intensity.
In the particle picture, the energy carried by each photon is proportional to its frequency. The bands of frequency present in a given EM signal may be sharply defined, as is seen in atomic spectra, or may be broad, as in blackbody radiation. ĮM radiation can have various frequencies. These two views are completely equivalent and are reconciled to one another in quantum field theory (see wave-particle duality). Alternatively, EM radiation can be viewed as an electromagnetic wave, which carries energy in its oscillating electric and magnetic fields. Cherenkov radiation glowing in the core of a TRIGA reactor.īecause electromagnetic (EM) radiation can be conceptualized as a stream of photons, radiant energy can be viewed as photon energy – the energy carried by these photons.
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