Nuclei Mock Test – Class 12 Physics

1. Consider the following statements about .
I. It is an energy.
II. It is approximately .
III. It is the same physical quantity as .
Which statements are valid?

2. A radioactive source has activity . Using , its activity in is:

3. For , take , , , and . The binding energy per nucleon is closest to:

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

5. A full nuclei problem asks for the most reliable stability comparison between two nuclides, then asks whether a reaction between them releases energy. The best method is:

6. Study the table and identify the row that best matches the neutron-proton trend.

7. A compact derivation gives and . The expression for nuclear density is:

8. In beta plus decay, the basic nucleon-level change is:

9. Three nuclei are represented only by their mass numbers: , , and . If the radius law is used, the order of their radii is:

10. A pure radioactive isotope has mass , molar mass , and half-life . Taking , , and , its activity after is closest to:

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

12. In forming a stable nucleus from separated nucleons, the final nuclear mass becomes smaller. The missing mass appears mainly as:

13. A mass defect is reported as . Using and , the energy equivalent is closest to:

14. A proposed reaction has product mass greater than reactant mass. What does this imply about its -value?

15. A proposed explanation says, “The nucleus is held together by gravity between protons and neutrons.” The best response is:

16. A nucleus changes from to . If only alpha and beta minus decays are involved, the minimum set of changes is:

17. In an alpha decay, the alpha particle is usually observed with a definite energy rather than a broad continuous range. This is mainly because:

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

19. A claim says, “In alpha decay, the daughter nucleus has the same chemical element as the parent because only energy is emitted.” The best evaluation is:

20. In alpha decay, the emitted particle is:

21. The deuterium-tritium fusion reaction emits a neutron along with a helium nucleus. One practical importance of the emitted neutron is that it:

22. Consider the statements below.
I. Binding energy is released when separated nucleons form a bound nucleus.
II. The same amount of energy must be supplied to separate the bound nucleus into free nucleons.
III. Binding energy is unrelated to mass defect.
Which statements are valid?

23. Consider the following statements about isotopes.
I. Isotopes of an element have the same .
II. Isotopes of an element always have the same .
III. Neutral isotopes of an element have the same number of electrons.
Which statements are valid?

24. Assertion: Nuclear force is called a short-range force.
Reason: It becomes negligible at distances much larger than a few .

25. The emission that consists of nuclei is called:

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

27. Consider the following statements about binding energy per nucleon.
I. It is calculated as .
II. It is usually a better stability indicator than total for comparing different-sized nuclei.
III. It is found by multiplying by .
Which statements are valid?

28. A straight-line graph of against time is obtained for a radioactive sample. If the slope is , the half-life is closest to:

29. A neutral atom has atomic mass . If electron binding energies are neglected, the approximate nuclear mass is:

30. A neutral atom has and atomic mass . Taking and neglecting electron binding energy, its approximate nuclear mass is:

31. The graph description below is used for a stability comparison.

The most reasonable ranking of average nuclear stability is:

32. In the notation , the upper number and lower number represent, respectively:

33. Assertion: and are expected to show very similar chemical behaviour.
Reason: Their neutral atoms have the same electronic configuration because they have the same .

34. In scattering experiments used to estimate nuclear size, a probe particle or wave must have a wavelength comparable with:

35. A point-like gamma source is observed from farther away while shielding and source strength remain unchanged. Increasing distance reduces exposure mainly because:

36. Read the case below and answer the question.

What remains the same for the two species?

37. The missing particle in the equation below is:

38. A parent nucleus emits an alpha particle. The daughter nucleus has:

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

40. A nucleus with is very heavy. A stability argument says it needs many neutrons. The best reason is:

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

42. For light stable nuclei, the usual neutron-proton relation is approximately:

43. Nuclear fission is best described as:

44. A radioactive source has and activity . The number of undecayed nuclei present is:

45. A nucleus has the same mass number as but one less proton. Its notation is best represented by:

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

47. A statement says, “The actual mass of a nucleus is equal to the exact sum of the masses of its free protons and neutrons.” The best evaluation is:

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

49. 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?

50. 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?