It is exploited in radar technologies utilized by police and meteorologists, though it is perhaps best observed when the frequency of a siren increases and decreases as it passes an observer.
Due to this phenomenon, the Breit-Wigner formula must be altered in practical use. It contributes a negative temperature coefficient of reactivity to uranium-fueled nuclear reactors, since it increases U-238's absorption cross-section through its namesake broadening; because that same broadening applies to spectral lines, the formula for this effect can be applied to spectra to determine gas temperatures. It can be used for non-invasive flow measurements, as in echocardiograms. An instance of it is redshift. It is exploited in radar technologies utilized by police and meteorologists, though it is perhaps best observed when the frequency of a siren increases and decreases as it passes an observer. FTP, name this effect, a shift discovered in 1842 by its namesake Dutch scientist.
Due to this phenomenon, the Breit-Wigner formula must be altered in practical use.
the Doppler effect [or Doppler shift]