The Resistivity of Copper at 20ºC Is 1 $\times$ 10^-8 $\Omega$ · M and the Number of Electrons Per Cubic Centimeter

Multiple Choice

The resistivity of copper at 20ºC is 1.7 $\times$ 10^-8 $\Omega$ · m and the number of electrons per cubic centimeter is 8.47 $\times$ 10²².If you take the average speed of the electrons to be equal to their root-mean-square speed (at T = 300 K) of 1.17 $\times$ 10⁵ m/s,it follows that their mean free path, $\lambda$ ,must be

A) 1.23 nm
B) 1.86 nm
C) 2.35 nm
D) 2.89 nm
E) None of these is correct.