Purpose:Show explicitly how two waves with the same amplitude and frequency will interfere when their relative phase changes.
Description:The University of Maryland 12-channel Fourier synthesizer is used with two fundamental frequencies (N=1) and their sum (top trace, scale not the same) displayed on the oscilloscope. As the phase of either signal is changed the two components go in and out of phase and the sum wave changes amplitude. The sequence of photographs below show the addition of the waves as they move in opposite directions by 22.5o steps (center trace to the left, bottom trace to the right). The sum wave from the synthesizer is fed into a loudspeaker to provide audible as well as visual evidence of the interference.