Dear all, I have inquiries about the Bohr's calculation for energy loss of charged particles. These inquires are from the "Techniques for Nuclear and Particle Physics Experiments" (W.Leo). On page 23 of this book, it is written that: the the interaction time is t = b/(γv), with b is the distance of atomic electron from the trajectory of incident particle and v is the velocity of incident particle. orbital period of electron is τ = 1/ν, with ν is the orbital frequency of atomic electron Why the interaction time of incident particle and atomic electron is t = b/v ? Does it means that it is considered as head-on collision ? It so, how about the electric force and Lorentz force that can be happen since incident particle and electron are both charged ? It is written that t = b/(γv) ≤ τ = 1/ν, and the reason is just for the interaction between incident charged particle and atomic electron can happen, isn't it ? Thank you so much.