Infrared, Visible Light and Soft Ultraviolet Radiation – Introduction
Non-ionizing electromagnetic radiation covers a wide range of frequencies – from extremely low frequencies (ELF), which include frequencies utilized in the electricity grid, through radiofrequencies (RF) to soft ultraviolet (UV).
An important range of non-ionizing radiation is the one which includes infrared, visible, and soft ultraviolet light. This range of frequencies, especially visible light, is very important to daily life. Radiation in these frequencies may be from natural or artificial sources.
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The electromagnetic spectrum between radio frequencies and X-rays |
The following are the wavelength and frequency ranges of infrared light, visible light and soft UV:
Infrared (IR) range
Wavelengths in this range are shorter than those of RF and longer than those of visible light. They are measured in micron units, represented by the Greek letter µ (1 micron equals to one thousandth millimeter).
The infrared range is usually divided into sub-ranges that include long and intermediate infrared (3-14 µ), short infrared (1.4-3 µ), and near infrared (0.75-1.4 µ). This is the classification used by the International Commission on Illumination (CIE). Infrared radiation is used in applications such as lasers, medical imaging, computer accessories (e.g. mouse), etc.
Visible light (VL) range
Visible light wavelengths can be perceived by the average human eye. Visible light wavelengths are measured in nanometers (1 nm equals one thousandth micron or one millionth millimeter) and range between 380 and 700 nanometers. The frequencies of the visible light range are 430-790 TeraHertz (THz).
Visible light comprises a color spectrum that can be seen by diffraction through a prism, or in the rainbow. They undergo a gradual change from the longest wavelength of about 700 nm (red light) to the shortest wavelength of about 380nm (violet light). The succession of colors is: red, orange, yellow, green, blue, and violet, and all possible intermediate colors. This frequency range is used for lighting, TV and computer screens, optical communication, solar cells, etc.
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Visible light as a succession of colors seen by diffraction through a prism |
Soft ultraviolet (UV) range
The UV range is defined as the spectral band from 380 to 10 nm, corresponding to 790 THz- 30 Peta Hz (PHz). It comprises three main sub-ranges: UVA (380-315 nm), UVB (315-280 nm) and UVC (280-100 nm). In addition, there is also UV radiation that is higher than UVC (below 121.6 nm). The range of UV between 380-121.6 nm, considered as soft UV, is within the range of non-ionizing radiation and the range below 121.6 nm is usually defined as ionizing UV, and is included in the ionizing radiation range of the electromagnetic radiation spectrum. The range of short UV wavelengths emitted by the sun is almost completely absorbed in the ionosphere – the uppermost layer of the atmosphere.
The UV range is extremely important with respect to health effects on humans – see Chapter on Policy. Among its uses: medical treatments (dental and other), hygiene and beauty care (purification of drinking water, sunbeds, etc.), medical research, and military applications.
The frequency range comprising infrared, visible light and UV has infinite applications in human daily life, as illustrated on the electromagnetic spectrum on the TNUDA Home Page and in the Table of Frequencies and their Uses.
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Testing validity of a banknote by UV light |
References
- Butcher G. Tour of the electromagnetic spectrum. National Aeronautics and Space Administration. Available at: http://missionscience.nasa.gov/ems/TourOfEMS_Booklet_Web.pdf
- The electromagnetic spectrum. Available at: http://csep10.phys.utk.edu/astr162/lect/light/spectrum.html
- Introduction to the electromagnetic spectrum (Finkenthal D., ed.). General Atomics. 1996. Available at: http://fusioned.gat.com/images/pdf/EMcurriculum.pdf
