Atoms Mock Test – Class 12 Physics

1. A hydrogen atom initially in absorbs a photon of energy . Since the ionisation energy from is , the kinetic energy of the emitted electron is

2. A one-electron ion emits a photon in the transition . Its photon energy is equal to the hydrogen photon energy. The value of is

3. Combining Bohr’s angular momentum rule with the circular force-balance condition is mainly used to derive

4. A claim says, “Bohr’s model failed completely, so it has no useful value.” The better evaluation is that Bohr’s model

5. The main purpose of an atomic model is to describe

6. In a comparison of atomic spectra, a line spectrum differs from a continuous spectrum because a line spectrum has

7. For absorption in Bohr’s model, the electron moves upward from energy to energy , where . The absorbed photon must satisfy

8. In the context of atomic models, an electron revolving around a nucleus is undergoing accelerated motion because

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

10. Use the energy-level description below.

The transition that emits the longest-wavelength photon is

11. The first line of the Paschen series corresponds to the transition

12. A data sheet lists the following conversion: . The energy in joules is

13. Starting with , if increases with , the speed must vary as for hydrogen because

14. The allowed radius of the orbit in a hydrogen-like atom is

15. A hydrogen atom initially in absorbs a photon of wavelength . Using , the atom can be excited to

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

17. A circular electron orbit has circumference . In the de Broglie standing-wave picture, the orbit corresponds to

18. For a hydrogen-like ion, and . If is doubled and is also doubled, then

19. The key difference between Rutherford’s and Bohr’s treatment of a revolving electron is that Bohr’s model states that the electron

20. A table compares Rutherford’s model and Bohr’s model.

The row that needs correction is

21. In Bohr’s circular orbit, the centripetal force needed by the electron is supplied by

22. In a Rutherford-scattering comparison, doubling the foil thickness approximately increases the number of scattered alpha particles because

23. Hydrogen gas gives a line spectrum rather than a continuous spectrum. This means that hydrogen atoms

24. The statement “an atom is neutral, so it contains no charged particles” is flawed because

25. For , the transition emits a photon. Using , its wavelength is closest to

26. The experimental chamber was evacuated in Rutherford’s scattering experiment mainly to

27. Classical electromagnetic theory predicts that an electron revolving around a nucleus should

28. In a Bohr orbit, the electron’s angular momentum is , and the orbit radius is . If the atom is hydrogen, the electron speed is

29. A graph is described below.

The plotted points should lie at

30. In a head-on approach of an -particle toward a positive nucleus, the deflection is maximum because

31. The main reason Bohr’s model was not just a repetition of Rutherford’s model is that Bohr added

32. A graph description is given below.

If the graph represents atomic and nuclear sizes, the correct identification is

33. A thin foil and an evacuated chamber are both used in the scattering experiment. Their common purpose is to

34. In the Bohr model, an excited state is a state for which

35. The usual order of atomic radius is about , while the usual order of nuclear radius is about . This comparison shows that

36. For the same orbit number , the radius of compared with hydrogen is

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

38. A hydrogen-like ion means an ion that

39. In head-on alpha scattering, the relation is useful for estimating

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

41. A photon has energy . Using , its energy in is

42. In Bohr’s model, radiation is emitted when the electron

43. Assertion: Bohr’s model is more successful than Rutherford’s model in explaining the hydrogen spectrum.
Reason: Bohr’s model introduces discrete stationary energy states and photon emission during transitions.

44. For head-on alpha scattering from the same nucleus, the initial kinetic energy is doubled. The new distance of closest approach becomes

45. Two Rutherford scattering cases use the same target and the same scattering angle. Case P uses -particles of kinetic energy , while Case Q uses -particles of kinetic energy . If the scattered count varies as , then is

46. Study the apparatus-function table and choose the fully matched row.

47. The small correction ignored in the simplest introductory Bohr formula for hydrogen is mainly due to

48. Assertion: Rutherford’s model could not explain the observed stability of atoms.
Reason: According to classical theory, an accelerated charged electron should radiate energy while revolving.

49. The radius of the second Bohr orbit of hydrogen is

50. Use the arrangement described below.

The largest deflection is expected for