= Mean free time between collisions Let 1/t be the mean probability per unit time that a conduc- tion electron in a metal collides with (or is scattered by) lattice vibrations, impurities, or defects, etc. Then the probability that an electron makes a collision in a small time interval dt is 8t/t. Suppose that n(t) is the concentration of electrons that have not yet collided. The change on in the uncollided electron concentration is then ndt/t. Thus, on = -ndt/t, or on = -8t/t. We can integrate this from n = n, at x = 0 to n = n(t) at time t to find the concentration of uncollided electrons n(t) at t n(t) = - n,exp(-t/t) [2.84] Show that the mean free time and mean square free time are given by Stn(t)dt 5,00t?n(t)dt t= and t = = 272 [2.85] Sn(t)dt Son(t)dt What is your conclusion? =T =