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 α-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 α-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 α-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 α-particles by a thin foil?

Question

Philoid · Accepted Answer

(a) The average angle of deflection of α-particles by a thin gold foil predicted by Thomson’s model about the same as that predicted by Rutherford’s model. This is due to the reason that, in both Thomson and Rutherford model of an atom, the average angle of deflection was taken.

(b) The probability of backward scattering (i.e., scattering of α-particles at angles greater than 90°) predicted by Thomson’s model much less than that predicted by Rutherford’s model.

(c) With increase in the thickness of, the number of target atoms that will increase. This will lead to increase in the collisions, and as we know, scattering is due to single collision. Therefore, with increase in thickness, the chances of collisions increase.