Relativistic Momentum

$$\vec{p}={\gamma }_{\text{total}}m\vec{v}$$ $${\gamma }_{\text{total}}=\frac{1}{\sqrt{1-\frac{{\text{v}}_{\text{total}}^2}{c^2}}}$$

For massless particles $p=\frac{E}{c}=\frac{h\nu }{c}=\frac{h}{\lambda }=\hslash k$

See Also

Relativistic Energy de Broglie Equation