For electromagnetic waves, it results in redshift.
The proximity fuse, developed during World War II, applies this principle to detonate automatically when the target is close enough. Since light waves do not travel through a medium, they require the relativistic form of this, which takes into account time dilation. The classical form was tested and confirmed for sound (*) waves in 1845 by Dutch scientist C.H.D. Buys Ballot.  For electromagnetic waves, it results in redshift. It relates the transmitted and observed frequencies of a wave in terms of its velocity and the velocity of its source. FTP, name this physical phenomenon that causes the pitch of the siren on a passing police car to change relative to a stationary observer.
The proximity fuse, developed during World War II, applies this principle to detonate automatically when the target is close enough.
{Doppler} effect or {shift}