Every particle with momentum p corresponds to a matter wave of wavelength λ.
Symbols
λ
matter wavelength
[m]
h
Planck's constant
[J·s]
p
particle momentum
[kg·m/s]
Where it comes from
Not only light, but also particles (electrons) have a wave nature. The greater the momentum, the shorter the wavelength — which is why for macroscopic bodies the wave is immeasurably small.
When to use it
Quantum mechanics, electron microscope, electron diffraction.
Example
An electron with momentum p=2⋅10−24 kg·m/s. Calculate the wavelength (h=6.63⋅10−34).