Hi all, Edit: Here's the question, in case you guys don't have the book: In the Drude moel the probability of the electron suffering a collision in any infinintesimal interval dt is just dt/T. a) show that an electron picked at random at a given moment had no collision during the preceding t seconds with the probability exp[-t/T]. Show that it will have no collision during the next t seconds with the same probability. I'm trying to figure out how to get the exp[-t/T] part, 'cause nowhere in the chapter does it show a probability as XX exp[-t/T]. Please just help me get started. Any reference equations would be good... Thanks!