Nuclei Mock Test – Class 12 Physics

1. A radioactive isotope has molar mass . A sample of mass is pure isotope and has half-life . Taking and , its initial activity is closest to:

2. A graph of nuclear force between two nucleons against their separation is described below.

The description mainly shows that nuclear force:

3. Match each classification with its defining condition.

4. A mass calculation uses neutral atomic masses for both sides of a nuclear reaction. Why can electron masses often cancel out in such a calculation?

5. A detector records activity from a gamma source even after a paper sheet and an aluminium sheet are placed between the source and detector. The best interpretation is:

6. A mass defect is found to be . Using , the corresponding energy is closest to:

7. A reactor operator withdraws control rods slightly from a steady reactor core. The expected immediate nuclear effect is:

8. A reactor produces of thermal power. Each fission releases , and . The fission rate is closest to:

9. A nuclide has , , and binding energy per nucleon . Taking , , and , its neutral atomic mass is closest to:

10. A source emits radiation that causes strong ionisation in a very short path. A second source emits radiation that is detected after passing through thick shielding more easily. The best comparison is:

11. When neutral atomic masses are used to calculate binding energy, a convenient formula for mass defect is:

12. Match each radioactive emission with its basic identity.

13. The notation and the notation are both seen in a text. If is known to have , why is still understandable?

14. On the curve, both useful fission of very heavy nuclei and useful fusion of very light nuclei move products:

15. A light nucleus moves by fusion toward a product with a larger . The energy release is explained by:

16. Electron capture changes a nucleus in a way similar to beta plus decay because it:

17. A parent nucleus undergoes two alpha decays followed by one beta minus decay. The net change in mass number and atomic number is:

18. A detector is placed near three sources of nuclear radiation. Source P produces heavy charged particles, source Q produces light negatively charged particles, and source R produces neutral photons. The sources are most likely emitting:

19. A student says, “Fission and fusion are opposite processes, so one must always absorb energy if the other releases energy.” The best response is:

20. A neutral atom is represented by . The element symbol is not named, but the numbers are given. The nuclear charge is:

21. A thermal reactor runs for one day. Take energy per fission , , and molar mass of . The mass of fissioned is closest to:

22. The alpha decay equation is mainly based on conservation of:

23. For a nucleus with , , , , and , the binding energy is closest to:

24. Read the case below and answer the question.

What remains the same for the two species?

25. A reactor condition is described by the following table.

The correct row is:

26. A radioactive sample has a larger decay constant than another isotope. Compared under the same initial number of nuclei, the sample with larger has:

27. A graph of binding energy per nucleon against mass number is used instead of a graph of total against mainly because:

28. The binding energy per nucleon of is unusually high among very light nuclei. This mainly indicates that :

29. A graph-description question uses this information:

Why does this graph alone not directly rank nuclear stability across all nuclei?

30. Assertion: Heavy stable nuclei usually have more neutrons than protons.
Reason: Neutrons contribute to nuclear attraction but do not increase Coulomb repulsion.

31. Radioactivity is best described as:

32. A parent nucleus at rest emits an alpha particle. The daughter nucleus recoils mainly because of conservation of:

33. A mass entry in a nuclear data table is written as . Using , what is this mass in ?

34. The masses of a proton, a neutron, and an electron are compared. The best qualitative order is:

35. After time , a sample's activity changes from to . The expression for is:

36. A source emits particles with charge . The radiation is deflected in an electric field toward the positive plate. The most suitable identification is:

37. A radioactive sample contains two independent isotopes P and Q. At , their activities are and , respectively. The half-lives are for P and for Q. The total activity after is:

38. An endoergic nuclear reaction has . The target nucleus is initially at rest. Which statement about the projectile energy is most appropriate?

39. The integrated form of the radioactive decay equation is:

40. A reaction is balanced. The unknown nucleus is:

41. Match the reactor component with its main function.

42. Half-life is the time in which:

43. Read the situation below and answer the question.

What does this show about individual radioactive decay?

44. Consider the following statements about nuclear power and radioactive materials.
I. Control rods regulate a fission chain reaction by absorbing neutrons.
II. A moderator is mainly used to slow down neutrons.
III. Radioactive waste handling depends on activity and half-life.
Which statements are valid?

45. The strong nuclear force is needed inside a nucleus mainly because:

46. A reactor uses fission energy to generate electricity. Which energy conversion sequence is most suitable?

47. A tracer isotope used for observation should usually have a half-life that is:

48. A radioactive material emits alpha particles. Outside the body, a sheet of paper can stop much of this radiation, but it can still be dangerous if the material enters the body. The reason is:

49. Match the nuclear terms with their meanings.

50. The statement “radioactive decay is random but still follows a precise law for a large sample” is best explained by saying that: