Answer the following questions, which help you to understand the difference between Thomson's model and Rutherford's model better.
a. Is the average angle of deflection of a-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 a-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
b. Much less
c. It suggests that the scattering is predominantly due to a single collision, because the • chance of a single collision increases linearly with the number of target atoms, and hence linearly with thickness.
d. In Thomson.s model, a single collision causes very little deflection. The observed average scattering angle can be explained only by considering multiple scattering. So it is wrong to ignore multiple scattering in Thomson.s model. In Rutherford.s model, most of the scattering comes through a single collision and multiple scattering effects can be ignored as a first approximation.