Atoms Mock Test – Class 12 Physics

1. The energy of a photon emitted in a Bohr transition depends on

2. If is doubled and is kept unchanged in a hydrogen-like atom, the orbital radius becomes

3. A table lists changes in head-on scattering conditions.

The row that gives the wrong effect on is

4. A symbolic derivation uses two relations:
I.
II.
Together, these relations show that allowed radii are not arbitrary because

5. An -particle approaching a gold nucleus is deflected because

6. A hydrogen atom in is just ionised by a photon whose threshold wavelength is closest to , using . The energy threshold used in this calculation is

7. In atomic physics, a photon is best described as

8. The radius of the orbit of , where , is

9. The energy of the level of hydrogen is

10. Rutherford’s nuclear model could not explain atomic stability because a revolving electron is

11. The expected path of an electron in Rutherford’s model under classical radiation loss is best described as

12. For , an electron moves from an orbit of radius to an orbit of radius . The emitted photon energy is

13. The kinetic energy of the electron in the Bohr orbit is related to its speed by

14. Compare the hydrogen-like species in the table.

For the emitted photon energies, the correct order is

15. If an electron wave around a proposed circular orbit contains wavelengths around the circumference, the orbit is not allowed in the Bohr-de Broglie picture because

16. For , an electron occupies the orbit whose radius is . The total energy of the electron is

17. A hydrogen atom changes from an energy level to . The energy of the emitted photon is

18. A graph description is given below.

The rapid fall of with indicates that

19. The Rydberg constant appears in the hydrogen spectrum formula. Its usual SI unit is

20. A neutral atom has . The number of electrons in it is

21. In alpha scattering, the closest-approach condition for a head-on case is based on the idea that, momentarily,

22. For corresponding transitions in hydrogen and , such as , the wavelength for is

23. Compare two Bohr orbits:

The ratio is

24. A hydrogen atom in absorbs a photon of energy . The best conclusion is that

25. For a fixed value of , increasing in the Rydberg formula makes the spectral lines of that series approach

26. For a fixed target nucleus, an -particle passing closer to the nucleus suffers a larger deflection mainly because

27. A hydrogen line has wavenumber . The transition is represented by

28. The hydrogen line has wavelength approximately . For the corresponding transition in , the wavelength is approximately

29. A student compares kinetic energy and potential energy in atomic models. Kinetic energy is most directly associated with

30. If a hydrogen atom in the ground state absorbs a photon of energy , the kinetic energy of the freed electron is

31. For the same transition, a one-electron ion emits a photon whose frequency is times the hydrogen frequency. The ion’s nuclear charge number is

32. A compact conclusion that correctly compares the three early atomic models is

33. Bohr’s radius formula and speed formula show opposite dependences on because

34. Assertion: Thomson’s model was able to explain the electrical neutrality of atoms.
Reason: In Thomson’s model, electrons were embedded in a sphere of positive charge.

35. Two alpha particles have the same kinetic energy and approach the same nucleus. Particle P has impact parameter , while particle Q has impact parameter . The more strongly deflected particle is

36. Consider the two statements below.
I. Thomson’s model could explain the overall neutrality of an atom.
II. Thomson’s model could explain large-angle alpha-particle scattering by a tiny dense nucleus.

37. Bohr’s first postulate about stationary orbits was needed because classical theory predicted that a revolving electron should

38. The first line of a hydrogen spectral series has the

39. Starting from the Bohr relations and , the reason finally varies as is that

40. For the Balmer first line of hydrogen, and . The wavenumber is

41. A table compares observations with models.

The row that needs correction is

42. The Bohr radius is the radius of

43. An atomic model that includes charged particles, circular motion, and radiation must be able to deal with all of the following ideas except

44. For hydrogen, compare the photon emitted in with the photon emitted in . The ratio of their energies is

45. Assertion: In Bohr’s model, angular momentum of the electron is quantised.
Reason: The allowed values satisfy , where .

46. As increases for hydrogen, the total energy

47. In atomic calculations, the energy unit is commonly used because atomic energy changes are

48. A spectral line is produced by a transition ending at in hydrogen. The line belongs to the

49. A head-on alpha-scattering case has initial kinetic energy . The target nucleus has charge . The alpha particle has charge . The electrostatic potential energy at closest approach is

50. The direction of force on an -particle near a positive nucleus is