Primer on the Quantum Theory of the Atom ... a Chem1 Reference Text

Two other attributes of waves are the amplitude (the height of the wave crests with respect to the base line) and the phase, which measures the position of a crest with respect to some fixed point. The square of the amplitude gives the intensity of the wave: the energy transmitted per unit time). λ u ν -= A unique property of waves is their ability to combine constructively or destructively, depending on the relative phases of the combining waves.