• 1.6: Superposition and Interference

    When two or more waves travel through the same medium at the same time, the waves pass through each other without being disturbed. The net disturbance or displacement of the medium is simply the sum of the individual wave displacements. This is true of waves that are finite in length (wave pulses) or continuous sine waves.

    When the crests and troughs of the two waves are precisely aligned, the superposition produces pure constructive interference. Pure constructive interference produces a wave that has twice the amplitude of the individual waves but has the same wavelength.

    On the other hand, destructive interference occurs when two identical waves arrive at the same point and are exactly out of phase (aligned crest to trough). Because the disturbances are in the opposite direction for this superposition, the amplitude is zero for pure destructive interference: the waves completely cancel each other out.