Type of Frequency Wavelength Type of transition radiation range (Hz) range g-rays 1020-1024 <10-12 m nuclear x-rays 1017-1020 1 nm-1 pm inner electron ultraviolet 1015-1017 400 nm-1 nm outer electron visible 4-7.5x1014 750 nm-400 nm outer electron near-infrared 1012-4x1014 2.5 µm-750 nm outer electron, molecular vibrations infrared 1011-1012 25 µm-2.5 µm molecular vibrations microwaves 108-1012 1 mm-25 µm molecular rotations, electron spin flips* radio waves 100-108 >1 mm nuclear spin flips* *energy levels split by a magnetic field
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