An Etymological Dictionary of Astronomy and Astrophysics
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The → electromagnetic radiation with the longest → wavelengths (and lowest energies), ranging from 0.3 mm to several km. Radio waves form a very broad category, which includes the → submillimeter waves (with a wavelength of 0.3-1 mm) and → microwave regions (1 mm to several cm).

→ radio; → wave.

The → electromagnetic radiation with a wavelength ranging from 1 mm to several 100 km. See so → radio wave.

→ radio; → wavelength.