Nuclei Mock Test – Class 12 Physics

1. A reaction releases per event. The energy per event in , using , is:

2. Match each classification with its defining condition.

3. A bound nucleus has binding energy . If it is completely separated into its individual nucleons, the minimum energy supplied should be:

4. Rutherford-type alpha scattering gave strong evidence that an atom contains:

5. A sample has half-life . The time required for its activity to become of its initial value is:

6. Beta minus particles emitted from a radioactive source show a continuous energy spectrum. The reason is that:

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

8. The unit of activity, becquerel, is equivalent to:

9. A fusion process has products with lower binding energy per nucleon than the reactants. The process would not release energy on this basis because:

10. A nuclear reaction has . The most suitable interpretation is:

11. When a nucleus undergoes beta minus decay, the daughter nucleus has:

12. A fission reaction produces two fragments and several neutrons. The total binding energy of all products is larger than that of the initial nucleus by . The reaction energy is best described as:

13. Very high temperature is required for thermonuclear fusion because the nuclei must:

14. A decay equation is written as . The main error is that:

15. Consider the following statements about shielding.
I. Paper is usually enough to stop alpha particles.
II. Aluminium is commonly used to reduce beta particles.
III. Gamma rays are best stopped completely by a single sheet of paper.
Which statements are valid?

16. A radioactive source is chosen for a medical tracer study lasting a few hours. The isotope has a half-life of several days. What is the main concern with this choice?

17. A graph of against for nuclei is a straight line with slope . Using the radius law, the radius of a nucleus with is:

18. Assertion: Alpha particles have low penetrating power but high ionising power.
Reason: Alpha particles are relatively massive and carry charge .

19. A heavy nucleus splits into two medium-mass fragments. If the fragments have higher than the original heavy nucleus, the process can release energy because:

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

21. A compact comparison says:

The sequence P, Q, R is:

22. Radioactivity is best described as:

23. The approximate charge independence of nuclear force is best illustrated by saying that:

24. A beta source is placed near a thin paper sheet and then near an aluminium sheet. The paper has little effect, but aluminium reduces the count strongly. This behaviour is most consistent with:

25. The moderator in a thermal nuclear reactor is used mainly to:

26. The table gives four descriptions of mass defect and binding energy. Identify the row with the physically valid statement.

27. Study the table and identify the row that gives the correct classification.

28. 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?

29. A graph of against for a radioactive sample is exponential. The tangent to the curve is steeper near than at later times because:

30. A nucleus far from the band of stability is generally expected to:

31. The relation is useful because it connects:

32. In a simplified scattering picture, most alpha particles pass almost straight through a thin foil, while a few are deflected through large angles. This pattern suggests that:

33. If , then the activity at time is:

34. A fission fragment pair is not unique for fission. This means:

35. A graph of the number of undecayed nuclei against time for a radioactive sample should be:

36. Fusion of light nuclei requires very high temperature mainly because:

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

38. A mass difference of is converted into energy. Use . The energy equivalent is:

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

40. The pair and should be classified as:

41. A radioactive sample is chemically combined with another substance. Its decay rate remains practically unchanged. This observation supports the idea that radioactivity:

42. A scattering observation shows that the nuclear charge is not spread over the whole atomic radius. This observation is most consistent with:

43. In a nuclear reaction, the -value is most directly the:

44. A nucleus contains several protons very close together. If only electrostatic force acted among them, the protons would:

45. Neutral atomic masses are used for an alpha decay. Given , , , and , the alpha-decay -value is closest to:

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

47. For a nucleus represented by , if is the nuclear mass, the mass defect can be written as:

48. Consider the following statements about nuclear force.
I. It is much stronger than Coulomb repulsion at nuclear distances.
II. It has a range comparable with ordinary atomic radius.
III. It is attractive at normal nuclear separation but repulsive at extremely small separation.
Which statements are valid?

49. A mass-energy calculation gives . The energy in should be found from:

50. A proton-rich nucleus lies below the band of stability on an -versus- graph. A likely way for it to move toward stability is: