Radiant energy

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Radiant energy is the energy transported by electromagnetic waves. The term is most commonly used in the fields of solar energy, heating and lighting, but is also used less frequently in other fields (such as telecommunications). The quantity of radiant energy may be calculated by integrating radiant power with respect to time and, like all forms of energy, its SI unit is the joule.

Contents

Analysis

Because electromagnetic (EM) radiation can be considered as consisting of photons, radiant energy can be viewed as the energy carried by these photons. The radiation emitted by radiating bodies is concentrated in certain portions of the electromagnetic spectrum. Such radiation bands may be sharply defined, as is seen in star spectra, or may be more diffuse. EM radiation has three principal components: wavelength and frequency, which are strictly inversely proportional, and intensity, which determines the amount of energy carried by the radiation. Radiant energy may originate in a body or be reflected from another body (in which case it may be refracted or otherwise modified).

Open systems

Radiant energy is one of the energy sources that can be used to power an open system. Such an open system can be man-made (such as a solar energy collector), or natural, such as the Earth's atmosphere. In geophysics, transparent greenhouse gases trap the sun's radiant energy (at certain wavelengths), allowing it to penetrate deep into the atmosphere or all the way to the Earth's surface, where they are re-emitted as longer wavelength radiation (chiefly infrared radiation). Radiant energy produced in the sun is a result of nuclear fusion.

Applications and patents

Radiant energy, as well as convective and conductive energy, is used for heating homes. It can be generated electrically by infrared lamps, or can be absorbed from sunlight and used to heat water. Since radiant energy is really just electromagnetic radiation under another name, it is the basis of a wide range of communication technologies using radiofrequency and microwave radiation.

One of the earliest wireless telephones to be based on radiant energy was invented by Nikola Tesla. The device used transmitters and receivers whose resonances were tuned to the same frequency, allowing communication between them. In 1916, he recounted (see Anderson's book, below) an experiment he had done in 1896. He recalled that "Whenever I received the effects of a transmitter, one of the simplest ways [to detect the wireless transmissions] was to apply a magnetic field to currents generated in a conductor, and when I did so, the low frequency gave audible notes."

The United States Patent Offices has a classification of radiant energy for patent applications (Class 250, a residual class for methods and apparatus involving radiant energy). This class provides for all methods and apparatus for using, generating, controlling or detecting radiant energy, combinations including such methods or apparatus, subcombinations of same and accessories therefore not classifiable elsewhere by the patent office. [1]

SI radiometry units

Template:SI radiometry units

See also

Template:Radio spectrum Template:EMSpectrum

Main

Science

References and external articles

Regulations
Patents
  • Template:US patent - Apparatus for the utilization of radiant energy - N. Tesla
  • Template:US patent - Method of utilizing of radiant energy - N. Tesla
  • Template:US patent - Method of generating electricity from radiant energy called variable polarizability capacity generator - L. R. O'Hare
Other
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