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. 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.
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Analysis
Because elctromagnetic (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.
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.
One of the earliest wireless telephones was based on radiant energy. The device had its resonance tuned to a particular frequency of other repeaters to communicate between each. According to Nikola Tesla, it was the "... [S]implest ways [to detect the radiant energy ...] the low frequency gave audible notes. [... in a field, there was] placed a conductor, a wire or a coil, and then [Tesla] would get a note [...] characteristics of the audible note".
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] (http://www.uspto.gov/go/classification/uspc250/defs250.htm)
SI radiometry units
See also
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Radio spectrum |
| Electromagnetic Spectrum
Radio waves | Microwave | Terahertz radiation | Infrared | Optical spectrum | Ultraviolet | X-ray | Gamma ray Visible: Red | Orange | Yellow | Green | Blue | Indigo | Violet |
Main
- Shortwave radiation
- Longwave radiation
- Federal Standard 1037C
- Transmission
- Telephone
- Schumann resonance
Science
- Zero-point energy
- Power
- Radiometry
- Photoelectric effect
- Ionizing radiation
- Open system
- Cosmic microwave background radiation
References and external links
- Caverly, Donald Philip, "Primer of electronics and radiant energy" New York, McGraw-Hill, 1952.
- Hardis, Jonathan E., "Visibility of Radiant Energy (http://nvl.nist.gov/pub/nistpubs/sp958-lide/025-027.pdf.)". PDF.
- "Radiant energy (http://www.its.bldrdoc.gov/fs-1037/dir-029/_4341.htm)". FS-1037C.
- Lighting Design Knowledgebase (http://www.schorsch.com/kbase/glossary/radiant_energy.html)