For 10 points, identify this quantity obtained by dividing velocity by frequency, which has units of distance.
The cross-section for Rayleigh scattering is proportional to the inverse-fourth power of this quantity, and Compton scattering results in a change of this quantity given by Planck's constant over the product of electron mass and the speed of light, times one minus the cosine of scattering angle. This quantity increases for photons climbing out of gravitational potential wells according to the integrated Sachs-Wolfe effect, and the ratio between the observed and emitted values for this quantity, minus one, defines the redshift. This quantity increases for sound when the source of the sound is moving away from a stationary observer in the Doppler effect. For 10 points, identify this quantity obtained by dividing velocity by frequency, which has units of distance.
The cross-section for Rayleigh scattering is proportional to the inverse-fourth power of this quantity, and Compton scattering results in a change of this quantity given by Planck's constant over the product of electron mass and the speed of light, times one minus the cosine of scattering angle.
wavelength