CBSE 2025 · Region 5 · Set 1 · Q16 · 1 mark
Assertion (A) : In Rutherford's alpha particle scattering experiment, the presence of only few alpha particles at angle of scattering $\displaystyle \pi$ led him to the discovery of nucleus. Reason $\displaystyle (R)$: The size of nucleus is approximately $\displaystyle 10^{-5}$ times the size of an atom and therefore only few alpha particles are rebounded.
Official answer
From CBSE’s own marking scheme for this paper.
(A)
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
AtomsAlpha-particle Scattering and Rutherford’s Nuclear Model of AtomUnderstandassertion_reasonmedium
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CBSE Class 12 Physics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.