= de Broglie relations
{c}
{{wiki=Matter_wave#de_Broglie_relations}}
Relates particle momentum and its wavelength, or equivalently, energy and frequency.
The wavelength relation is:
$$
\lambda = \frac{h}{p}
$$
but since:
$$
v = \lambda f
E = p v
$$
the wavelength relation implies:
$$
\frac{v}{f} = \frac{h}{p}
f = \frac{v p}{h} = \frac{E}{h}
$$
Particle wavelength can be for example measured very directly on a <double-slit experiment>.
So if we take for example electrons of different speeds, we should be able to see the diffraction pattern change accordingly.