Nuclei Mock Test – Class 12 Physics

1. The radioactive decay law begins from the idea that the number of nuclei decaying per unit time is proportional to:

2. A source emits radiation that is not deflected by an electric field and has very high penetrating power. The most likely radiation is:

3. A nucleus undergoes alpha decay and forms a daughter nucleus in an excited state. The daughter then emits a gamma ray and reaches its ground state. What changes during the gamma emission step?

4. A nuclear data line gives , , , , and . The mass defect is closest to:

5. The pair and should be classified as:

6. The saturation of nuclear force helps explain why the binding energy per nucleon for many medium and heavy nuclei is:

7. If a nucleus with mass number is compared with another nucleus having mass number , the density ratio predicted by the simple radius law is:

8. In beta minus decay, the nuclear change at the nucleon level is best represented as:

9. Gamma rays can pass through matter more effectively than alpha particles mainly because gamma rays:

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

11. Consider the following statements about nuclear density.
I. It is nearly the same for light and heavy nuclei.
II. It is nearly constant because .
III. It is extremely large compared with ordinary matter density.
Which statements are valid?

12. 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:

13. The activity of a radioactive sample is defined as:

14. A beta minus decay equation is balanced without writing the antineutrino. Why is the antineutrino still physically important?

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

16. When a nucleus undergoes alpha decay, its daughter nucleus has:

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

18. A nucleus contains protons and neutrons. If is its actual nuclear mass, the mass defect is written as:

19. In a controlled nuclear reactor, the purpose of control rods is to:

20. A fusion reaction has total reactant mass and total product mass . Its energy release is closest to:

21. A decay equation is proposed:

The equation is:

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

23. A nuclear reaction conserves and , but its products are left in an excited nuclear state and then emit a gamma ray. The gamma ray mainly carries away:

24. Consider the three changes below.

The sequence P, Q, R is:

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

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

27. A row in a nuclear-change table is shown below.

Which row correctly describes beta minus decay?

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

29. A heavy nucleus with and fissions into fragments with , , and , , plus two free neutrons. Ignoring neutron kinetic energy in the binding comparison, the energy released is closest to:

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

31. 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?

32. Match the radiation-safety action with the main physical idea.

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

34. A nucleus with has binding energy per nucleon . Its total binding energy is:

35. A radiation source must be handled with shielding, and the main concern is highly penetrating neutral radiation. The most suitable shield among the following is:

36. A nucleus emits radiation and changes from to at a lower energy state. The emitted radiation is most likely:

37. A pair of nuclei is described as follows:

The relation between the two nuclei is:

38. In the reaction , neutral atomic masses can be used directly for the -value because:

39. Heavy stable nuclei generally require mainly because:

40. A nucleus has total binding energy and mass number . Its binding energy per nucleon is:

41. A qualitative band of stability is plotted with neutron number on the vertical axis and proton number on the horizontal axis. For large , the band bends above the line . This means:

42. A pure radioactive sample has mass , molar mass , and half-life . Taking , the number of undecayed nuclei after is:

43. A sealed alpha source is safer to handle externally than an unsealed alpha-emitting powder mainly because:

44. Match the nuclear terms with their meanings.

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

46. A nucleus has , , and total binding energy . It splits into two identical fragments, each with and binding energy per nucleon . On binding-energy grounds, this split would:

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

48. A distance of is equal to:

49. A graph-description question uses this information:

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

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