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 `alpha`-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 `alpha`-particles scattered at moderate angles is proportional to t. What clue does this linear dependence on t provide?
(d) In which model is it completely wrong to ignore multiple scattering for the calculation of average angle of scattering of `alpha` -particles by a thin foil?

Explanation

(a) About the same as we are considering the average angle of deflection.
(b) Much less as there is no massive centre, i.e. nucleus in Thomson.s model.
(c) It indicates that scattering is mainly due to a single collision, because the chance of a single collision increases linearly with the increase in the number of the target atoms and that increases linearly with the thickness of the foil.
(d)In Thomson.s model, there is very little deflection due to a single collision. The average scattering angle that is observed can be explained only by considering multiple scattering. So it is completely wrong to ignore multiple scattering in Thomson.s model.
However, in Rutherford.s model, a single collision brings about most of the scattering and multiple scattering effects can be ignored as a first approximation.