For 10 points, give this term referring to the distortion of the observed frequency of waves, particularly but not necessarily light, due to velocity.
The Ives-Stilwell experiment explored the possibilities of its transverse variety, which requires the introduction of the Lorentz factor. Its cosmological variety results from the predictions of Hubble's Law, and its relativistic variety comes with a coefficient of the square root of the quantity one minus beta over one plus beta, but at non-relativistic speeds its effects are proportional to radial velocity. For 10 points, give this term referring to the distortion of the observed frequency of waves, particularly but not necessarily light, due to velocity.
The Ives-Stilwell experiment explored the possibilities of its transverse variety, which requires the introduction of the Lorentz factor.
Doppler effect [prompt on redshift]