Nuclei Mock Test – Class 12 Physics

1. A calculation starts with a nuclear mass and wants the approximate neutral atomic mass of the same nuclide. If electron binding energy is neglected, the suitable expression is:

2. In the proton-proton fusion process in stars, hydrogen nuclei ultimately form helium nuclei. The energy release is explained by:

3. In stars, gravity is important for fusion because it:

4. A nuclide has , , and is neutral as an atom. Choose the complete composition statement.

5. Using , , , , and , the binding energy is closest to:

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

7. A radioactive nucleus emits a gamma ray after an alpha or beta decay has left it in an excited state. The gamma emission mainly:

8. For a reaction written as reactants products, the -value using masses is:

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

10. Consider the following statements about , , and .
I. A larger means a shorter half-life.
II. .
III. Mean life is always smaller than half-life.
Which statements are valid?

11. A nucleus with has binding energy per nucleon . It splits into two identical fragments, each with and binding energy per nucleon . The energy change for this split is:

12. A nucleus is described as having and nuclear charge . Its nuclide notation must have:

13. 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?

14. A table gives four possible nuclear reactions. Identify the balanced reaction.

15. A missing particle is to be found in the nuclear equation:

If the decay is beta minus decay, the missing particle is:

16. A nuclear reaction has total initial mass and total final mass . Using , the -value and reaction type are:

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

18. A claim says, “A larger total binding energy always means a nucleus is more stable than every nucleus with smaller total binding energy.” The most careful response is:

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

20. A fusion reaction has products with total binding energy greater than that of the reactants. Ignoring other losses, the energy released is:

21. If the mass number of a nucleus becomes times larger, what happens to its nuclear volume according to ?

22. The nuclear radius relation implies that nuclear volume is proportional to:

23. A proposed nuclear change has products with smaller total binding energy than the reactants, while the total number of nucleons remains the same. What does this suggest about energy?

24. 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?

25. A nuclear reaction is studied with the reactants initially at rest. The total rest mass of the reactants is , and the total rest mass of the products is also . No external energy is supplied, but the products are claimed to have extra kinetic energy. Which conclusion is most appropriate?

26. A sample's activity falls from to in . Its half-life is:

27. Gamma radiation is best identified as:

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

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

30. A mass table lists a neutral atomic mass and a nuclear mass for the same nuclide. The nuclear mass is smaller mainly because it does not include:

31. The nuclear charge of an atom with atomic number is:

32. A atom has . Take , , and . Its binding energy is closest to:

33. During a short observation of a sample with a very long half-life, its activity appears nearly constant because:

34. The nuclear force becomes strongly repulsive at extremely small separations between nucleons. This repulsive core is important because it:

35. A calculation for a stable nucleus gives . What is wrong with this setup?

36. A fusion plasma must be confined for a useful time because:

37. Study the table and identify the row that correctly connects a region of the curve with the energy-releasing process.

38. Two possible nuclear changes are listed below.

What is common to both changes?

39. A row of a nuclear-decay table is shown below.

Which row is correct?

40. 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?

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

42. A reaction product has a higher binding energy per nucleon but the reaction has according to the complete mass data. The safest conclusion is:

43. 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:

44. For the pair and , the most useful comparison is:

45. The relation between mass defect and binding energy is sometimes misunderstood as “mass defect is a loss of matter from the nucleus.” A better interpretation is:

46. Read the case below and answer the question.

What remains the same for the two species?

47. A sample has activity . If , its activity is:

48. A nucleus decays by alpha emission. The equation is best written as:

49. The short range of nuclear force means that it is effective mainly over distances of about:

50. A reaction is written in the form . In this notation: