MODERN PHYSICS

QUIZ-2

Atomic Structure and its History (a) Assumes that the angular momentum of
electrons is quantized
16. The existence of a positively charged nucleus in an
(b) Uses Einstein’s photoelectric equation
atom was first suggested by the experiment of
(c) Predicts continuous emission spectra for atoms
(a) J J Thomson (b) E Rutherford
(c) Chadwick (d) Hahn and Strassman (d) Predicts the same emission spectra for all types
17. The Rutherford -particle experiment shows that of atoms
most of the -particles pass through almost 24. The ratio of the energies of the hydrogen atom in
undeflected while some are scattered through large the first to the second excited state
angles. What information does it give about the (a) 4 : 1 (b) 1 : 4
structure of the atom? (c) 4 : 9 (d) 9 : 4
(a) Atom is hollow 25. The ground state energy of hydrogen atom is – 13.6
(b) The whole mass of the atom is concentrated in a eV. When its electron is in the first excited state, its
small centre called nucleus excitation energy is
(c) Nucleus is positively charged (a) 3.4 eV (b) 6.8 eV
(d) All the above (c) 10.2 eV (d) zero
2+
1 2
26. Energy required for the electron excitation in Li
18. An alpha nucleus of energy mv bombards a from the first to the third Bohr orbit is
2
heavy nuclear target of charge Ze. Then the (a) 36.3 eV (b) 108.8 eV
distance of closest approach for the alpha nucleus (c) 122.4 eV (d) 12.1 eV
will be proportional to 27. The ionization energy of hydrogen atom is 13.6 eV.
2 Following Bohr’s theory, the energy corresponding
(a) v (b) 1/m
to a transition between 3rd and 4th orbit is
1 1
(c) 4 (d) (a) 3.40 eV (b) 1.51 eV
v Ze (c) 0.85 eV (d) 0.66 eV
19. In a Rutherford scattering experiment, when a 28. In Bohr’s model, the atomic radius of the first orbit
projectile of charge Z1 and mass M1 approaches a is r0 , then the radius of the third orbit is
target nucleus of charge Z2 and mass M2, the (a) r0/9 (b) r0
distance of closest approach is r0. The energy of the (c) 9r0 (d) 3r0
projectile is
29. The ground state energy of hydrogen atom is –13.6
(a) directly proportional to M1 × M2
eV. When its electron is in the first excited state, its
(b) directly proportional to Z1 Z2
excitation energy is
(c) inversely proportional to Z1
(a) 3.4 eV (b) 6.8 eV
(d) directly proportional to mass M1
(c) 10.2 eV (d) zero
20. An –particle of energy 5 MeV is scattered
30. In terms of Bohr radius a0, the radius of the second
through 180° by a fixed uranium nucleus. The
Bohr orbit of a hydrogen atom is given by
distance of the closet approach is of the order of
–10 (a) 4a0 (b) 8a0
(a) 1 Å (b) 10 cm
–12
(c) 10 cm
–15
(d) 10 cm (c) 2 a0 (d) 2a0
Bohr's Atomic Model 31. To explain his theory, Bohr used
21. The total energy of electron in the ground state of (a) Conservation of linear momentum
hydrogen atom is –13.6 eV. The kinetic energy of (b) Quantization of angular momentum
an electron in the first excited state is (c) Conservation of quantum frequency
(a) 3.4 eV (b) 6.8 eV (d) Conservation of energy
(c) 13.6 eV (d) 1.7 eV
22. The spectral series of the hydrogen atom that lies in 32. According to Bohr’s theory of hydrogen atom, for
the visible region of the electromagnetic spectrum the electron in the nth allowed orbit the
(a) Paschen (b) Balmer I. linear momentum is proportional to 1/n.
(c) Lyman (d) Brackett II. radius is proportional to n.
23. The Bohr model of atoms
III. kinetic energy is proportional to 1/n 2 .

IV. angular momentum is proportional to n.

 Choose the correct option from the codes given (a) Its kinetic energy increases and its potential
below and total energy decreases
(b) Its kinetic energy decreases, potential energy
(a) I, III and IV (b) only I
increases and its total energy remains the same
(c) I and II (d) only III
33. Energy E of a hydrogen atom with principal (c) Its kinetic and total energy decreases and its
−13.6 potential energy increases
quantum number n is given by E = eV. The (d) Its kinetic, potential and total energy decreases
n 2+
energy of a photon ejected when the electron jumps 42. A hydrogen atom and a Li ion are both in the
from n = 3 state to n = 2 state of hydrogen, is second excited state. If LH and LLi are their
approximately respective electronic angular momenta, and E H and
(a) 1.5 eV (b) 0.85 eV ELi their respective energies, then
(c) 3.4 eV (d) 1.9 eV (a) LH>LLi and |EH| > |ELi|
34. Which of the following transitions in hydrogen
(b) LH = LLi and |EH| < |ELi|
atoms emit photons of highest frequency?
(c) LH = LLi and |EH| > |ELi|
(a) n = 2 to n = 6 (b) n = 6 to n = 2
(c) n = 2 to n = 1 (d) n = 1 to n = 2 (d) LH<LLi and |EH| < |ELi|
35. If 13.6 eV energy is required to ionize the 43. Ionization potential of hydrogen atom is 13.6 eV.
hydrogen atom, then the energy required to remove Hydrogen atoms in the ground state are excited by
an electron from n = 2 is monochromatic radiation of photon energy 12.1
(a) 10.2 eV (b) zero eV. According to Bohr’s theory, the spectral lines
(c) 3.4 eV (d) 6.8 eV emitted by hydrogen will be
36. Which of the following transitions gives photon of (a) two (b) three
maximum energy? (c) four (d) one
(a) n = 1 to n = 2 (b) n = 2 to n = 1 44. An electron makes transition inside a hydrogen
(c) n = 2 to n = 6 (d) n = 6 to n = 2 atom. The orbital angular momentum of the
37. Find the ratio of ionization energy of Bohr’s electron may change by
hydrogen atom and hydrogen-like lithium atom. h
(a) h (b)
(a) 1/9 (b) 7/9 
(c) 1/3 (d) none of the above
h h
38. The state of the triply ionized beryllium (Be3+) that (c) (d)
8 4
has the same orbital radius as that of the ground
45. In Bohr’s Model of hydrogen atom. The ratio
state of hydrogen is
between the period of revolution of an electron in
(a) 4 (b) 1
orbit of n = 1 to the period of revolution of the
(c) 2 (d) 3
electron in the orbit n = 2
39. The transition from the state n = 3 to n = 1 in a
(a) 1 : 2 (b) 2 : 1
hydrogen like atom results in ultraviolet radiation.
(c) 1 : 4 (d) 1 : 8
Infrared radiation will be obtained in the transition
46. The ionization energy of the electron in the
from
hydrogen atom in its ground state is 13.6 eV. The
(a) 4 → 3 (b) 2 → 1
atoms are excited to higher energy levels to emit
(c) 3 → 2 (d) 4 → 2 radiations of 6 wavelengths. Maximum wavelength
40. Ratio of longest wavelengths corresponding to of emitted radiation corresponds to the transition
Lyman and Balmer series in hydrogen spectrum is : between
(a) n =3 to n = 2 states (b) n = 3 to n = 1 states
9 5 (c) n = 2 to n = 1 states (d) n = 4 to n = 3 states
(a) (b)
31 27 47. Electron in hydrogen atom first jumps from third
3 7 excited state to second excited state and then from
(c) (d)
23 29 second excited to the first excited state. The ratio of
41. The electron in a hydrogen atom makes a transition the wavelength 1 : 2 emitted in the two cases is:
from an excited state to the ground state. Which of 20 7
the following statement is true? (a) (b)
7 5
 27 27 55. The energy levels of the hydrogen spectrum is
(c) (d)
20 5 shown in figure. There are some transitions A, B, C,
48. Hydrogen atoms are excited from ground state of D and E. Transition A, B and C respectively
the principal quantum number 4. Then the number represent
of spectral lines observed will be
(a) 3 (b) 6
(c) 5 (d) 2
49. Consider an electron in the nth orbit of a hydrogen
atom in the Bohr model. The circumference of the
orbit can be expressed in terms of de-Broglie
wavelength  of that electron as
(a) (0.529) n (b) n
(c) (13.6)  (b) n
50. An electron jumps from the 4th orbit to the 2nd orbit (a) First member of Lyman series, third spectral
of hydrogen atom. Given the Rydberg’s constant R
line of Balmer series and the second spectral
= 105 cm–1. The frequency in Hz of the emitted line of Paschen series
radiation will be (b) Ionization potential of hydrogen, second
3 3
(a) 105 (b) 1015 spectral line of Balmer series and third spectral
16 16 line of Paschen series
9 3 (c) Series limit of Lyman series, third spectral line
(c) 1015 (d)  10
15

16 4 of Balmer series and second spectral line of

51. A ground-state electron (in a hydrogen atom) Paschen series
absorb a photon of energy 3E0. How much kinetic (d) Series limit of Lyman series, second spectral
energy does the electron now have? ( E0 is the line of Balmer series and third spectral line of
energy in the ground state of electron Paschen series
(a) E0 (b) 2E0 56. An energy of 24.6 eV is required to remove one of
(c) 3E0 (d) 4 E0 the electrons from a neutral helium atom. The
energy (in eV) required to remove both the
52. The ratio of areas between the electron orbits for
electrons from a neutral helium atom is
the first excited state to the ground state for the
(a) 79.0 (b) 51.8
hydrogen atom is
(c) 49.2 (d) 38.2
(a) 2 : 1 (b) 4 : 1
(c) 8 : 1 (d) 16 : 1
53. An electron in the hydrogen atom jumps from
excited state n to the ground state. The wavelength
so emitted illuminates a photosensitive material
having work function 2.75 eV. If the stopping
potential of the photoelectron is 10 V, then the
value of n is
(a) 5 (b) 2
(c) 3 (d) 4
54. An electrons of a stationary hydrogen atom passes
from the fifth energy level to the ground level. The
velocity that the atom acquired as a result of
photons emission will be:
24 24 h R
(a) (b)
25h R 25m
25h R 25m
(c) (d)
24 m 24 h R
(m is the mass of the electron, R, Rydberg constant
and h, Plank’s constant)