In the following equation, the Doppler shift (denoted by the letter \(z\)) is calculated by comparing (i.e., taking the ratio of) the difference (\(\Delta\lambda\)) between the observed wavelength (\(...In the following equation, the Doppler shift (denoted by the letter \(z\)) is calculated by comparing (i.e., taking the ratio of) the difference (\(\Delta\lambda\)) between the observed wavelength (\(\lambda_{obs}\)) and the rest wavelength (\(\lambda\)). If the observed wavelength is longer than the rest wavelength, the shift is called “redshift.” On the other hand, if the object is moving toward the observer, \(z\) will be negative, and so will the velocity.
