I have a question that's been gnawing at me recently. In classical physics, momentum is mass times velocity, which makes sense, take the mass of an object, calculate the velocity and you are left with a vector quantity of momentum. In quantum physics, we have momentum p=h/λ. This doesn't seem to be a vector quantity and the mass and the velocity are both simply represented by a wavelength? Since this DeBroglie formula represents actual massive particles, how do we unpack a wavelength to find out the actual mass and velocity of the particle (say electron), as a vector quantity?