Atoms and molecules have temperature-caused random movements, so emission frequencies shift by Doppler effect {Doppler broadening}. Higher temperature makes more Doppler broadening. Higher mass makes less Doppler broadening. Higher frequency makes more Doppler broadening. Microwaves have lower frequencies than optical waves and so have lower Doppler broadening.
Physical Sciences>Physics>Matter>Atom>Wavelength Change>Doppler
5-Physics-Matter-Atom-Wavelength Change-Doppler
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Date Modified: 2022.0224