1. The problem statement, all variables and given/known data In the famous “Rutherford backscattering” experiment, alpha particles (Z=2) of approximately 7 MeV were used to bombard a Au (Z=79) film. Rutherford derived the scattering formula by treating an incident alpha particle and a Au target atom as two point charges with their charge numbers equal to their atomic numbers. This assumption, however, is not accurate in describing general ion solid interactions. Explain (a) why was Rutherford’s approach successful in his experiments? and (b) under what conditions deviation from Rutherford scattering formula will occur? 2. Relevant equations 3. The attempt at a solution a) Rutherford’s approach was successful because he used an extremely thin foil with a target nucleus much heavier than the incident alpha particles. b) If the foil was thicker and the target nucleus and incident alpha particle were of comparable mass, Rutherford would have observed increased ion-solid reaction types.