Question

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:

• A. A, B Only
• B. B, E Only
• C. C, D Only
• D. A, C, E Only

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
In Rutherford's experiment, alpha particles are fired at a gold foil. Most pass through, indicating the atom is mostly empty space. Rebounding (\( \theta \approx 180^\circ \)) occurs only when an alpha particle is repelled by a concentrated positive charge.

Step 2: Key Formula or Approach:
The scattering of alpha particles depends on the impact parameter \( b \). For large-angle scattering or rebounding, \( b \) must be very small, corresponding to a head-on collision path.

Step 3: Detailed Explanation:
Statement A: Correct. The nucleus is about \( 10^5 \) times smaller than the atom, making the "target" for rebounding very small.
Statement B: Incorrect. Alpha particles (\( +2e \)) and gold nuclei (\( +79e \)) have vastly different charges.
Statement C: Correct. Rebounding occurs when the impact parameter is nearly zero, which is rare.
Statement D: Incorrect. High kinetic energy would actually make them more likely to pass closer or penetrate, not specifically explain why "only a few" rebound.
Statement E: Correct. Head-on collisions lead to \( 180^\circ \) scattering, and these are rare due to the small size of the nucleus.
Thus, A, C, and E are the correct explanations.

Step 4: Final Answer:
The correct statements are A, C, and E.