Astronomy   View all facts   Glossary   Help

physical phenomena > process > physical process > optical process > radiation modification > wavelength shift > Doppler shift

Doppler shift
subject			fact

Doppler shift	has value the amount of shift is directly proportional to relative velocity
	has definition The alteration in frequency of electromagnetic radiation due to relative motion between the source and observer.
	has definition The apparent change of frequency or wavelength of radiation from an object due to its motion toward or away from us. If the object is receding the frequency is decreased and the wavelength is increased, i.e. becomes red-shifted.
	has definition Displacement of spectral lines in the radiation received from a source due to its relative motion along the line of sight. A motion of approach results in a blueshift; a motion of recession results in a redshift.
	has definition Effect on the wavelengths of light (or sound) emitted by a source at a distance that is increasing or decreasing in relation to the observer. If the distance is increasing, the wavelengths are "stretched" (the light received shifts towards the red end of the spectrum; sound received goes down in pitch). If the distance is increasing, the wavelengths are "squeezed" (the light received shifts towards the blue end of the spectrum; sound received goes up in pitch).
	has definition The alteration in frequency of electromagnetic radiation due to relative motion between the source and observer.
	has definition The change in frequency of a wave (light, sound, etc.) due to the relative motion of source and receiver.
	has definition The blueshift or redshift produced by an object's motion toward or away from us. If a star moves toward us, its light waves get compressed and its spectrum is blueshifted; if a star moves away from us, its light waves get stretched and its spectrum is redshifted. The Doppler shift allows astronomers to measure the radial velocities of stars. The Doppler shift is not responsible for the redshifts that most galaxies exhibit; that is a cosmological redshift.
	has definition Change in the apparent wavelength of radiation (e.g., light or sound) emitted by a moving body. A star moving away from the observer will appear to be radiating light at a lower frequency than if at rest; consequently, lines in the star's spectrum will be shifted toward the red (lower frequency) end of the spectrum. The existence of a direct relationship between the redshift of light from galaxies and their distances is the fundamental evidence for the expansion of the universe.
	has definition Displacement of spectral lines in the radiation received from a source due to its relative motion in the line of sight. Sources approaching (-) the observer are shifted toward the blue; those receding (+), toward the red. The Doppler shift makes it possible to determine the radial velocity and the rotation of stars.
	has definition The shift in the received frequency and wavelength of a sound wave or electromagnetic wave that occurs when either the source or the observer are in motion. Approach causes a shift toward shorter wavelengths and higher frequencies, called a blueshift. Recession has the opposite effect, called a redshift.
	is a kind of wavelength shift
wavelength shift	changes property frequency (and wavelength)
optical process	has domain optics

Kinds of Doppler shift :

• blueshift (2 facts) - The shift of spectral lines toward shorter wavelengths in the spectrum of an approaching source of radiation.
• redshift (3 facts) - The shift of spectral lines toward longer wavelengths in the spectrum of a receding source of radiation.