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By Brijesh Sharma
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Updated on 9 Oct 2025, 01:44 IST
CBSE Class 12 Physics Nuclei MCQs: Chapter 13 of the CBSE Class 12 Physics syllabus, titled Nuclei, introduces students to the structure, properties, and energy aspects of atomic nuclei. Practicing CBSE Class 12 Physics Chapter 13 Nuclei MCQs helps students build strong concepts and prepare better for the board and competitive exams. These nuclei class 12 mcqs are designed to test analytical thinking, and also helps to revise the full chapter quickly.
The chapter covers topics like nuclear force, mass defect, binding energy, radioactive decay and nuclear fission and fusion. With well-curated nuclei mcq class 12 sets, students can self-assess their understanding. Also, for in-depth understanding, ncert solutions for class 12 physics and class 12 physics notes are helpful. For better practice, this page include atoms and nuclei class 12 mcq and atoms class 12 mcq based on recent trends.
1. The radius of a nucleus is proportional to:
Answer: c) A1/3
Formula: R = R0A1/3, with R0 ≈ 1.2 fm.
2. The density of a nucleus is:
Answer: b) Independent of A
Mass ∝ A and volume ∝ A, hence density is roughly constant.
3. Nuclear force is:
Answer & Explanation
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Answer: c) Short-range and strong
Acts within about 1–2 fm and binds nucleons tightly.
4. Which is not a property of nuclear force?
Answer: c) Long-range force
Nuclear force is short-ranged with saturation.
5. Binding energy per nucleon for heavy stable nuclei is about:
6. Half-life of a radioactive element depends on:
Answer: d) Nature of nucleus
Half-life is intrinsic to the isotope and largely unaffected by external conditions.
7. Activity of a sample is directly proportional to:
Answer: b) Decay constant
Activity A = λN.
8. The SI unit of activity is:
Answer: c) Becquerel
1 Bq = 1 disintegration per second.
9. If half-life is 10 min, the fraction undecayed after 30 min is:
Answer: d) 1/8
Three half-lives: (1/2)3 = 1/8.
10. Carbon-14 is used in:
11. Mass defect is:
Answer: a) Loss in mass due to energy release
Δm = Zmp + (A−Z)mn − M.
12. Binding energy is given by:
Answer: b) Δm·c²
Einstein relation E = mc² applies to mass-equivalent energy.
13. Maximum binding energy per nucleon is found in:
Answer: b) Iron
Fe-56 is among the most tightly bound nuclei.
14. In nuclear fission, binding energy per nucleon:
Answer: a) Increases
Heavy nuclei split into smaller, more stable fragments.
15. In nuclear fusion, binding energy per nucleon:
16. Neutrons are commonly used in fission because they are:
Answer: b) Uncharged
No Coulomb repulsion from the nucleus.
17. A common fissile reactor fuel is:
Answer: a) U-235
U-235 sustains a thermal-neutron chain reaction.
18. The Sun is powered by:
Answer: b) Fusion
Hydrogen fusion to helium via pp chain and CNO cycles.
19. A moderator in a reactor is used to:
Answer: b) Slow down neutrons
Thermal neutrons increase fission probability in U-235.
20. A common moderator is:
21. Radioactive decay law:
Answer: a) N = N0e−λt
First-order decay in time.
22. Mean life τ relates to half-life T1/2 as:
Answer: a) τ = T1/2/ln2
Using τ = 1/λ and T1/2 = ln2/λ.
23. Radioactive decay is:
Answer: b) Random
Only probabilities are predictable for ensembles.
24. Energy released per U-235 fission is about:
Answer: c) 200 MeV
Typical fission yields ~200 MeV including kinetic and gamma energy.
25. The binding-energy curve explains stability of:
Answer: b) Medium nuclei
Maxima around A ≈ 56 indicate high stability.
26. In α-decay, the emitted particle has mass number and charge:
Answer: b) 4, 2
An alpha particle is a He-4 nucleus.
27. In β⁻ decay, a neutron converts into:
Answer: a) Proton + electron + antineutrino
n → p + e⁻ + ν̄e.
28. In β⁺ decay, a proton converts into:
Answer: a) Neutron + positron + neutrino
p → n + e⁺ + νe.
29. Gamma rays are emitted when a nucleus:
Answer: b) Changes energy state
γ emission follows transitions between nuclear energy levels.
30. A radioisotope used in medical diagnosis is:
31. If half-life of radium is 1600 years, mean life is:
Answer: b) 1155 years
τ = T1/2/ln2 ≈ 1600/0.693.
32. Activity A = 1000 Bq, decay constant λ = 0.01 s⁻¹. Number of nuclei N is:
Answer: a) 104
N = A/λ = 1000/0.01 = 10,000.
33. For 3 half-lives, the fraction left undecayed is:
Answer: c) 1/8
(1/2)3 = 1/8.
34. Binding energy of He-4 if mass defect Δm = 0.030 u:
Answer: b) 27.9 MeV
Using 1 u ≈ 931 MeV: 0.030 × 931 ≈ 27.9 MeV.
35. Average binding energy per nucleon of He-4 from Q34 is:
36. Stability of a nucleus is largely determined by:
Answer: b) Neutron-proton ratio
Stable nuclei lie near the valley of stability defined by N/Z.
37. Which decay increases Z by 1?
Answer: b) Beta minus
n → p increases atomic number by one.
38. Which decay decreases Z by 1?
Answer: c) Beta plus
p → n reduces atomic number by one.
39. Nuclear forces are mainly:
Answer: a) Central and charge-independent
Approximately same between nn, pp, and np pairs.
40. The binding-energy curve explains:
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MCQs help students test conceptual clarity, improve speed, and strengthen their understanding of nuclear physics topics like binding energy, radioactive decay, and nuclear reactions.
Students can refer to NCERT textbooks, previous year papers, and curated resources with ncert solutions for class 12 physics to practice verified questions.
Yes, they usually cover nuclear properties, mass defect, radioactivity, fission, and fusion, which are part of the CBSE Class 12 Physics syllabus.
First, revise concepts using class 12 physics notes, then solve mcq class 12 physics chapter 13 to check application of knowledge.
Yes, many nuclei mcq class 12 questions are framed in line with JEE and NEET exam patterns, making them valuable for both board and entrance exam preparation.