Electromagnetic spectrum

The varieties of electromagnetic radiation form a continuum known as the Electromagnetic Spectrum. Its broad categories are called

The only difference between these manifestions of electromagnetic radiation is due to differences in the frequency and wavelength of the oscillations. These two quantities are related by the formula
    (velocity) = (frequency) x (wavelength), which in this case reads c = f

The types of electromagnetic radiation are listed above in decreasing order of wavelength, and hence increasing order of frequency. (When we study a little quantum mechanics later in the course, we will learn that this is also the order of increasing energy for the individual photons.)

Comments on Regions of the Electromagnetic Spectrum -- adapted from http://calspace.ucsd.edu/ames144a/ch7/ch7.html

range (approx.)
range (approx.)
Long-wave radio   
>10 m
<3x107 hz Includes traditional AM radio region. These frequencies can travel long distances by multiple reflections between the surface of the earth and its ionosphere.
Short-wave radio 10 cm - 10 m 3x107 - 3x109 Used for TV, FM, and other communication purposes. Generally travels only relatively short distances because the ionosphere is transparent to it.
Microwave 1 mm - 10 cm 3x109 - 3x1011 Present limit of radio technology for most purposes.
Far infrared 30 mm - 1 mm 3x1011 - 1013 3 K radiation fills universe.
Thermal infrared 3 mm - 30 mm 1013 - 1014 Thermal emission of earth and planets.
Near infrared 700 nm - 3mm 1014 - 4x1014 Solar and stellar emission.
Visible 400 nm - 700nm 
(1.7 - 3 eV)
4x1014 -7x1014 Peak of solar radiation. Visible to human eye, standard photographic film and CCD video detectors.
Ultraviolet 200 nm - 400nm 
(3 - 6 eV)
7x1014 - 
Divided at 300 nm by atmospheric (ozone) cutoff. Appreciable solar flux causes sunburn.
Vacuum UV (EUV) 10 nm -  200 nm 
(6 - 120 eV)
1.5x1015 - 3x1016 Very strong absorption in matter, hence very difficult to observe.
X-rays 120 eV- 100keV 3x1016 - 3x1019 Produced by electron beams in X-ray tubes, and by inner atomic transitions. Progressively more penetrating as E increases, up to many centimeters in water.
g-rays 100 keV 3x1019 Produced by nuclear and other high energy processes. Can penetrate up to meters in water.

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