A reflected waveform, which in turn sets up a standing wave on a transmission line occurs any time there's an impedance mismatch between source and load.
At 50/60Hz powerline frequencies it's usually of little consequence, but it becomes very significant at radio frequencies, especially at UHF and above.
The ultimate is terminating an RF transmission line with a short or leaving it completely open circuit. For example, with a shorted line of a quarter-wavelength at the frequency in use, the source driving will "see" not a short, but an infinitely high impedance.
Such lines are often used in RF work as filters.
