The wavelength of a particle decreases as its speed increases. This is described by the de Broglie wavelength equation:

λ = h / p

where:

* λ is the de Broglie wavelength

* h is Planck's constant

* p is the momentum of the particle (mass x velocity)

Since momentum is directly proportional to velocity, as the speed increases, the momentum also increases. This leads to a smaller de Broglie wavelength.

In simpler terms: The faster a particle moves, the more "concentrated" its wave-like nature becomes, resulting in a shorter wavelength.