wave interference

The principle of superposition of waves superposition states that when two or more propagating waves of the same type are incident on the same point, the resultant amplitude at that point is equal to the vector sum of the amplitudes of the individual waves.

If a crest of a wave meets a crest of another wave of the same frequency at the same point, then the amplitude is the sum of the individual amplitudes. This is known as constructive interference. Constructive interference occurs when the phase difference between the waves is an even multiple of \[\pi\] or \[0^{\circ},360^{\circ},720^{\circ},\dots\], or simply in phase.

If a crest of one wave meets a trough of another wave, then the amplitude is equal to the difference in the individual amplitudes. This is known as destructive interference. Destructive interference on the other hand occurs when the phase difference between the waves is an odd multiple of \[\pi\] or \[180^{\circ},540^{\circ},\dots\], or simply out of phase.