De Broglie wave length

A photon of frequency $\nu$ carries momentum $p=h\nu/c$; since the speed of light satisfies $c=\nu\lambda$, this can equally be written $p=h/\lambda$, giving the photon's wavelength in terms of its momentum as

De Broglie's key insight was to treat this relation not as a special property of photons, but as a completely general one, applicable to any moving particle whatsoever -- massive or massless. For a material particle of mass $m$ moving with speed $v$ (and therefore momentum $p=mv$), the associated wavelength is likewise

$\lambda=\frac{h}{mv}=\frac{h}{p} \qquad (7.10)$ …