Marine Glossary

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electromagnetic spectrum

Used to describe the broad range of frequencies of electromagnetic radiation, one band of which is the radio waves (see radio frequency).

Electromagnetic radiation is one of the wonders of the physical world. It is made up bundles of electric and magnetic fields, which move through space at the speed of light. See G181 and G182 and the notes included there for a description of the waves.

The full spectrum varies from radio waves, at the lower-frequency end, on up through visible light, and on to x-rays and gamma rays. These are all the same physical objects, they only differ in the frequency of oscillation of the fields.

The Electromagnetic Spectrum
(roughly, borders are not well defined, and often overlap)

wave type frequency (exponent)

radio waves 1 Hz to 10(12) Hz
Infrared 10(12) Hz to 10(14) Hz
visible light 10(14) Hz to 10(15) Hz
ultraviolet 10(15) Hz to 10(17) Hz
x-rays 10(16) Hz to 10(21) Hz
gamma rays > 10(18) Hz

Note we can see the visible waves and feel the heat (infrared) waves, but we don't "hear" the radio waves. The electrical radio waves are received by radios which convert them into sound waves in the speakers.

See also discussion of analog vs. digital signals in G427.