(5-14)    ①  Multiplication gives us:

②  The reciprocal relationship between σp  and  σx  means that their product is a fundamental constant (remember that h is Planck's constant). The individual values of σp  and  σx  may be changed, depending on the range of angular wavenumbers that we include in the superposition, but the increased localisation that results from a broader range of k (smaller σx ) is exactly cancelled out by the larger σp . This result quantifies, therefore, Werner Heisenberg's assertion that there is  a fundamental limit to how precisely it is possible to know both the position and momentum of a particle.