Now consider the quantum theory of conduction. at low temperatures, with scattering by lattice vibrations (phonons) not yet important,  ~ t. the residual resistivity, 0, as t -> 0 (the text calls this “i ”) is dependent on scattering by defects (impurities, . if the lattice is ‘perfectly ordered’, then  can approach infinity (or at least the size of the metal.) the residual resistivity is a measure of the purity of the sample. a relatively good sample of cu has 0=2 10-11m. a.) if the fermi velocity, uf, of cu is 1.57 106 m/s, and =2 10-11m, according to eq. 10-25 what is the mean free path  in units of m? (assume cu is monovalent, i. e. each atom contributes 1 electron to the conduction.) (show how the units come out to give units of length in the end.)