The Electromagnetic Spectrum
Rutgers University Institute of Marine and Coastal Sciences
above image copied from http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec.html.960105
The electromagnetic spectrum consists of all forms of electromagnetic radiation, each corresponding to a different section, or band, of the spectrum. For example, one band includes radiation that our eardrums use to interpret sound. While another band, visible light, cosists of radiation our eyes use to "see" light (See Figure Above). Notice how small the visible band is compared to the rest of the spectrum. An explantion of our eye's sensitivity to this small band is includeed in the following page describing Blackbody Radiation. The wave is the basic component of electromagnetic radiation and is described by the following basic terms:
- Crest : The highest point of the wave.
- Trough : The lowest point of the wave.
- Amplitude : The height of the wave as measured between the trough and the crest.
- Wavelength : The distance between two identical points on the wave.
- Period : The time it takes for a wavelength to pass a stationary point.
- Frequency : The number of wavelengths that pass a point in a set period of time.
Some of the above terms are illustrated in the following diagram:
Since elctromagnetic radition is dependent upon wavelength, the wavelength of the radiation determines its location in the spectrum. The figure at the top of the page illustrates the range of possible wavelengths. The longer waves consiting of sound and microwaves are to the left and the shorter wavelengths including x-rays and ultraviolet light are to the right.
Satellites are now used as the eyes and ears of the scientific community. They are equiped with radiometers that measure electromagnetic radiation. The radiometers are designed to accurately small bands of the spectrum. Therefore a researcher must know what wavelengths of radiation need to be analyzed and design a sensor specific to that application. How does one choose relevant bands to analyze? Different disciplines require different bands of the spectrum. Oceanographers focus on radiation specific to the ocean surfaces. In addition, atmospheric radiation must be analyzed so that ocean measurements can be corrected for any changes that occur during the trip from the ocean surface to the satellite. The peaks of this radition will determine the specific bands teh radiometer measures.
Wavelength peaks for differnet applications are calculated using the theories of
BlackBody Radiation.(See Next Page)
Useful Electromagnetic Radiation Links:
NASA Electromagnetic Spectrum Tutorial
-An excellent reference for any other questions you may have. Yea right,
as if this explanation is not enough.
-A good description of the visible portion of the spectrum including an
overview of the entire sepctrum/h5>
Specific Regions of the Electromagnetic spectrum
-Description important properties of the major regions of the spectrum