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Engineering Exams RRB-JE CMA (Chemical and Metallurgical Assistant) Technical Abilities 2025 22.04.25 Paper-2 Shift-1 Hard +1 -0.33
When a beam of 5.5 MeV α-particles emitted from a ²¹⁴Bi₈₃ radioactive source is allowed to fall on a thin foil of gold of thickness 2.1 × 10–7 m, then what percentage of an incident α-particles scatter by more than 1°.
Correct Answer: D. 0.0014
Explanation: The Rutherford gold foil experiment demonstrated that while most alpha particles pass through the foil unaffected, a small fraction experiences significant deflection due to the concentrated positive charge of the nucleus. Experimental data showed that approximately 0.14% of the incident alpha particles are scattered by an angle of more than 1 degree. This observation supported the nuclear model of the atom, as it indicated that the majority of the atom's volume is empty space with a dense, positively charged center. Among the provided options, 0.14% correctly identifies the percentage of particles scattered beyond this specific threshold.
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