Nuclei Mock Test – Class 12 Physics

1. 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?

2. The quantity called binding energy of a nucleus is best defined as the energy required to:

3. In age estimation, a sample's present activity is of the activity of a fresh sample of the same amount of material. If the half-life is , the estimated age is:

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

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

6. If the mass number of a nucleus becomes times larger, the nuclear radius becomes:

7. A radioactive decay is written as . The particle must be:

8. The nearly constant density of nuclei is mainly explained by the fact that:

9. A problem asks for both the stability comparison of two nuclei and the energy released in a reaction between them. The most reliable combined approach is:

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

11. An isotope has mean life . Its half-life is approximately :

12. A radioactive sample initially contains twice as many undecayed nuclei as another sample of the same isotope. At the same instant, its initial decay rate is:

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

14. A nucleus has and . Its neutron-proton relation is best described as:

15. Using nuclear data , , , , and , the mass defect is:

16. A binding energy of has what mass equivalent in , using ?

17. A source has activity . The average number of decays in is:

18. A comparison table is prepared for fission and fusion.

Which row gives the correct comparison?

19. A fossil sample contains of the original radioactive carbon activity. The statement most directly supported is:

20. A nucleus with has radius when . Its approximate volume is:

21. If , then the activity at time is:

22. The fusion reaction

releases energy. Which explanation best connects this release with nuclear stability?

23. A radioactive sample has initial activity and decay constant . The number of decays during one mean life is closest to:

24. A mixed nuclear data record is shown below.

The daughter after the alpha decay and the meaning of are:

25. For undecayed nuclei and , the number of undecayed nuclei after is closest to :

26. The missing particle in the equation below is:

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

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

29. A fission equation is proposed:

The value of required by mass-number conservation is:

30. A classification note says:

The sequence Pair I, Pair II, Pair III is:

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

32. Two neutral atoms are isotopes of the same element. Which comparison must be true?

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 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:

35. A sample has initial activity . After a certain time, only of the original undecayed nuclei remain. Its activity at that time is:

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

37. A sample with activity and half-life has what activity after ?

38. A claim about says, “The lower number is the neutron number because neutrons are inside the nucleus.” What is the best evaluation of this claim?

39. A tracer experiment lasts about . Four isotopes have similar chemical behaviour and detectable emissions. The most suitable half-life among the following is likely:

40. In a reactor core, shielding is included mainly to:

41. The penetrating power order for alpha, beta, and gamma radiations is:

42. For a radioactive isotope, the relation between mean life and half-life is:

43. The nearly constant nuclear density of different nuclei is consistent with the idea that:

44. A radioactive dating measurement gives present activity times the activity of a fresh sample of the same isotope and same amount. If , the age is closest to :

45. A sample's activity falls from to in . What will its activity be after another ?

46. A claim says, “Radioactivity can be stopped by changing only the chemical compound of the radioactive element.” The best evaluation is:

47. Match the force or interaction idea with its role in nuclear binding.

48. In an alpha decay, the ground-state -value is . In one decay branch, the daughter nucleus is formed in an excited state of energy . Ignoring small recoil details, the energy available as kinetic energy of the alpha particle and daughter nucleus is:

49. In an electron-capture transition, neutral atomic masses give . The daughter is formed in an excited state of energy . Using , the energy left for the neutrino and recoil is closest to:

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