In Rutherford's alpha-particle scattering experiment, the rebounding of alpha particles (scattering angle ≈180∘) occurs when they undergo a head-on collision with the gold nucleus.
A head-on collision corresponds to an impact parameter close to zero. Since the size of the gold nucleus (≈10−15 m) is extremely small compared to the size of the gold atom (≈10−10 m), the effective target area is very small. Consequently, the probability of an alpha particle having a minimum impact parameter is very low.
Thus, only a few alpha particles undergo head-on collisions and rebound back. This makes statements A, C, and E correct.
Statement B is incorrect because the charge of an alpha particle is +2e while the charge of a gold nucleus is +79e.
Statement D is incorrect because the alpha particles emitted from the radioactive source have nearly the same kinetic energy.
Answer: A, C, E Only