Atoms & Nuclei

JEE Main level, single correct, medium

6 of 239

Question 6 of 239

In Rutherford's alpha-particle scattering experiment, only a few alpha particles rebound back because
A. The size of gold nucleus is very small as compared to the size of gold atom.
B. Alpha particle and gold nucleus have equal charge.
C. The impact parameter is minimum for a few alpha particles.
D. A few alpha particles have very high kinetic energy.
E. Only a few alpha particles undergo head-on collision with the nuclei.
Choose the correct answer from the options given below:

Show answer and solution

Answer: (D) A, C, E Only

In Rutherford's alpha-particle scattering experiment, the rebounding of alpha particles (scattering angle ≈180∘\approx 180^{\circ}) 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\approx 10^{-15} m) is extremely small compared to the size of the gold atom (≈10−10\approx 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+2e while the charge of a gold nucleus is +79e+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

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