question_answer 11)

Answer the following questions, which help you understand the difference between   Thomson's  model  and Rutherford's model better. (a) Is the average angle of deflection of particles by a thin gold foil predicted by Thomson's model much less, about the same, or much greater than that predicted by Rutherford's model ? (b) Is the probability of backward scattering (i.e., scattering of particles at angles greater than 90°) predicted by Thomson's model much less, about the same, or much greater than that predicted by Rutherford's model ? (c) Keeping other factors fixed, it is found experimentally that for small thickness t, the number of a-particles scattered at moderate angles is proportional to t. What clue does this linear independence on t provide ? (d) In which model is it completely wrong to ignore multiple scattering for the calculation of average angle of scattering of a-particles by a thin foil ?  

Answer:

(a) It is about the same because we are considering average deflection angle. (b) It is much less than the predicted value because the massive core is absent in Thomson's model. (c) It suggests that the scattering of particles is primarily because of the single collision. (d) In Thomson's model of atom. Multiple collisions are required to be considered in this model because positive charge is spread throughout in this model.