3. The number of neutrons in an atom of $_{90}Th^{230}$ is:
(A) 90
(B) 140
(C) 230
(D) 320
Multiple Choice
ID- 15298
4. The first model of an atom in 1998 was proposed by:
(A) Ernst Rutherford
(B) Albert Einstein
(C) J. J. Thomson
(D) Niels Bohr
Multiple Choice
ID- 15299
5. Rutherford's experiments suggested that the size of the nucleus is about:
(A) 10-14 m to 10-12
(B) 10-15 m to 10-13
(C) 10-15 m to 10-14
(D) 10-15 m to 10-12
Multiple Choice
ID- 15300
6. The Bohr model of atoms:
(A) assumes that the angular momentum of electrons is quantized
(B) uses Einstein's photoelectric equation
(C) predicts continuous emmision spectra for atoms
(D) predicts the same emmision spectra for all types of atoms
Multiple Choice
ID- 15301
7. In the Geiger-Marsden scattering experiment, the number of scattered particles detected are maximum and minimum at the scattering angles respectively at:
(A) 0° and 180°
(B) 180° and 0°
(C) 90° and 180°
(D) 45° and 90°
Multiple Choice
ID- 15302
8. In the Geiger-Marsden scattering experiment, in case of head-on collision the impact parameter should be:
(A) maximum
(B) minimum
(C) infinite
(D) zero
Multiple Choice
ID- 15303
9. In an atom the ratio of the radius of orbit of an electron to the radius of the nucleus is:
(A) 10³
(B) 10⁴
(C) 10⁵
(D) 10⁶
Multiple Choice
ID- 15304
10. The relation between the orbit radius and the electron velocity for a dynamically stable orbit in a hydrogen atom is (where all notations have their usual meanings):
(A) $v = \sqrt{\frac{4π\varepsilon_0}{me^2r}}$
(B) $r = \sqrt{\frac{e^2}{4π\varepsilon_0v}}$
(C) $v = \sqrt{\frac{e^2}{4π\varepsilon_0mr}}$
(D) $v = \sqrt{\frac{ve^2}{4π\varepsilon_0m}}$
Multiple Choice
ID- 15305
11. In a hydrogen atom, the total energy of an electron is:
(A) $\frac{e^2}{4π\varepsilon_0r}$
(B) $\frac{-e^2}{4π\varepsilon_0r}$
(C) $\frac{-e^2}{8π\varepsilon_0r}$
(D) $\frac{e^2}{8π\varepsilon_0r}$
Multiple Choice
ID- 15306
12. In which of the following systems will the radius of the first orbit (n + 1) be minimum?
(A) doubly ionized lithium
(B) singly ionized helium
(C) deuterium atom
(D) hydrogen atom
Multiple Choice
ID- 15307
13. When an atomic gas or vapour is excited at low pressure, by passing an electric current through it then:
(A) emission spectrum is observed
(B) absorption spectrum is observed
(C) band spectrum is observed
(D) Both B and C
Multiple Choice
ID- 15308
14. The moment of momentum for an electron in the second orbit of a hydrogen atom as per Bohr's model is:
(A) $\frac{h}{π}$
(B) $2πh$
(C) $\frac{2h}{π}$
(D) $\frac{π}{h}$
Multiple Choice
ID- 15309
15. The first spectral series was discovered by:
(A) Balmer
(B) Lyman
(C) Paschen
(D) Pfund
Multiple Choice
ID- 15310
16. Which of the following spectral series falls within the visible range of electromagnetic radiation:
(A) Lyman series
(B) Balmer series
(C) Paschen series
(D) Pfund series
Multiple Choice
ID- 15311
17. Which of the following statements is true for hydrogen atom?
(A) $\text{Angular momentum} ∝ \frac{1}{n}$
(B) $\text{Linear momentum} ∝ \frac{1}{n}$
(C) $\text{Radius} ∝ \frac{1}{n}$
(D) $\text{Energy} ∝ \frac{1}{n}$
Multiple Choice
ID- 15312
18. In the Geiger-Marsden scattering experiment, the trajectory traced by an α-particle depends on:
(A) number of collision
(B) number of scattered α-particles
(C) impact parameter
(D) None of these
Multiple Choice
ID- 15313
19. In the Bohr model of the hydrogen atom, the lowest orbit corresponds to:
(A) infinite energy
(B) maximum energy
(C) minimum energy
(D) zero energy
Multiple Choice
ID- 15314
20. The value of the ionisation energy of the hydrogen atom is:
(A) 3.4 eV
(B) 10.4 eV
(C) 12.09 eV
(D) 13.6 eV
Multiple Choice
ID- 15315
21. If n is the orbit number of the electron in a hydrogen atom, the correct statement among the following is:
(A) electron energy increases as $n$ increases
(B) hydrogen emits infrared rays for the electron transition from $n = ∞ $ to $n = 1$
(C) electron energy is zero for $n = 1$
(D) electron energy varies as $n^2$
Multiple Choice
ID- 15339
22. If there are $N$ atoms in a source of Laser light and each atom is emitting light with density $I$, then the total intensity produced by it is:
(A) $NI$
(B) $N^2I$
(C) $N^3I$
(D) $N^4I$
Multiple Choice
ID- 15340
23. If $13.6\,eV$ energy is required to separate a hydrogen atom into a proton and an electron, then the orbital radius of an electron in a hydrogen atom is:
(A) $5.3 × 10^{-11}\, m$
(B) $4.3 × 10^{-11}\, m$
(C) $6.3 × 10^{-11}\, m$
(D) $7.3 × 10^{-11}\, m$
Multiple Choice
ID- 15341
24. If $13.6\,eV$ energy is required to separate a hydrogen atom into a proton and an electron, then the value of the velocity of the revolving electron is:
(A) $1.2 × 10^6\, ms^{-1}$
(B) $2.2 × 10^6\, ms^{-1}$
(C) $3.2 × 10^6\, ms^{-1}$
(D) $4.2 × 10^6\, ms^{-1}$
Multiple Choice
ID- 15342
25. In Balmer series of an emission spectrum of hydrogen, the first four lines with different wavelengths $H_α\, H_β\, H_γ\, H_δ$ are obtained. Which line has the maximum frequency out of these?
(A) $H_α$
(B) $H_β$
(C) $H_γ$
(D) $H_δ$
Multiple Choice
ID- 15343
26. The energy required to excite an electron in a hydrogen atom to its first excited state is:
(A) $8.5\, eV$
(B) $10.2\, eV$
(C) $12.7\, eV$
(D) $13.6\, eV$
Multiple Choice
ID- 15344
27. The acronym LASER stands for:
(A) Light Amplification by Stimulated Emission of Radiation
(B) Light Amplitude by Stimulated Emission of Radiation
(C) Light Amplification by Strong Emission of Radiation
(D) Light Amplification by Stimulated Emission of Radiowave
Multiple Choice
ID- 15345
28. The shortest wavelength present in the Paschen series of spectral lines is:
(A) 720 nm
(B) 790 nm
(C) 800 nm
(D) 820 nm
Multiple Choice
ID- 15346
29. A hydrogen atom initially in the ground level absorbs a photon and is excited to $n = 4$ level then the wavelength of the photon is:
(A) 790 Å
(B) 870 Å
(C) 970 Å
(D) 1070 Å
Multiple Choice
ID- 15347
30. A hydrogen atom initially in the ground level absorbs a photon and is excited to $n = 4$ level then the frequency of the photon is:
(A) $3.1 × 10^{15}\, Hz$
(B) $3.1 × 10^{18}\, Hz$
(C) $9.1 × 10^{15}\, Hz$
(D) $9.1 × 10^{18}\, Hz$
Multiple Choice
ID- 15348
31. The relationship between kinetic energy ($K$) and potential energy ($U$) of an electron moving in an orbit around the nucleus is:
(A) $U = -K$
(B) $U = -2K$
(C) $U = -3K$
(D) $U = -\frac{1}{2}K$
Multiple Choice
ID- 15349
32. The $H$ atoms in the ground state collide inelastically. The maximum amount by which their combined kinetic energy is reduced is:
(A) $10.2\, eV$
(B) $20.4\, eV$
(C) $13.6\, eV$
(D) $27.2\, eV$
Multiple Choice
ID- 15350
33. The simple Bohr model is not applicable to $He^4$ atom because:
(A) $He^4$ is an inert gas
(B) $He^4$ has neutrons in the nucleus
(C) $He^4$ has more than one electron
(D) None of these
Multiple Choice
ID- 15351
34. A set of atoms in an excited state decays:
(A) in general to any of the states with lower energy
(B) into a lower state only when excited by an external electric field
(C) all together simultanesusly into a lower state
(D) to emit photons only when they collide
Multiple Choice
ID- 15352
35. The simple Bohr model cannot be directly applied to calculate the energy levels of an atom with many electrons. This is because:
(A) of the electrons not being subjected to a central force
(B) of the electrons colliding with each other
(C) of screening effects
(D) the force between the nucleus and an electron will no longer be given by Coulomb's law
Multiple Choice
ID- 15353
36. If $E$ is the energy of $n^{th}$ orbit of the hydrogen atom the energy of $n^{th}$ orbit of the $He$ atom will be:
(A) $E$
(B) $2E$
(C) $3E$
(D) $4E$
Multiple Choice
ID- 15354
37. The minimum energy that must be given to a $H$ atom in the ground state so that it can emit an $H_γ$ line in the Balmer series is:
(A) $12.4\, eV$
(B) $10.2\, eV$
(C) $13.06\, eV$
(D) $13.6\, eV$
Multiple Choice
ID- 15355
38. When an electron falls from higher energy to a lower energy level the difference in the energies appears in the form of:
(A) electromagnetic radiation only
(B) thermal radiation only
(C) both electromagnetic and thermal readiations
(D) None of these
Multiple Choice
ID- 15356
39. The volume occupied by an atom is greater than the volume of the nucleus by a factor of about:
(A) $10^1$
(B) $10^5$
(C) $10^{10}$
(D) $10^{15}$
Multiple Choice
ID- 15357
40. An ionised $H$ molecule consists of an electron and two protons. The protons are separated by a small distance of the order angstrom. In the ground state:
(A) the electron would not move in circular orbits
(B) the energy would be $(2)^4$ times that of a $H$-atom
(C) the molecule will soon decay into a proton and a $H$-atom
(D) None of these
Multiple Choice
ID- 15358
41. Consider aiming a beam of free electrons towards free protons. When they scatter, an electron and a proton cannot combine to produce an $H$-atom because of:
(A) energy conservation
(B) simultaneously releasing energy in the form of radiation
(C) momentum convervation
(D) angular momentum conservation
Multiple Choice
ID- 15359
BSEB, 2019 (A)
42. The solar spectrum is:
(A) Continuous
(B) Line spectrum
(C) Spectrum of black lines
(D) Spectrum of black bands
Multiple Choice
ID- 15360
BSEB, 2019 (A)
43. The energy of a photon of wavelength λ is:
(A) $hcλ$
(B) $\frac{hc}{λ}$
(C) $\frac{hλ}{c}$
(D) $\frac{λ}{hc}$
Multiple Choice
ID- 15361
44. $O_2$ molecule consists of two oxygen atoms. In the molecule, nuclear force between the nuclei of the two atoms:
(A) is not important because nuclear forces are short-ranged
(B) is as important as electrostatic force for binding the two atoms
(C) cancels the repulsive electrostatic force between the nuclei
(D) is not important because oxygen nucleus has equal number of neutrons and protons
Multiple Choice
ID- 15362
45. Out of the following which one is not a possible energy for a photon to be emitted by hydrogen atom according to Bohr's atomic model?
(A) $0.65\, eV$
(B) $1.9\, eV$
(C) $11.1\, eV$
(D) $13.6\, eV$
Multiple Choice
ID- 15363
46. In which of the following Bohr's orbit ($n$) a hydrogen atom emits the photons of lowest frequency?
(A) $n=2$ to $n=1$
(B) $n=4$ to $n=2$
(C) $n=4$ to $n=1$
(D) $n=4$ to $n=3$
Multiple Choice
ID- 15364
47. When an electron jumps from the fourth orbit to the second orbit, one gets the:
(A) second line of Paschen series
(B) second line of Balmer series
(C) first line of Pfund series
(D) second line of Lyman series
Multiple Choice
ID- 15365
48. The ratio of the speed of the electron in the ground state of hydrogen atom to the speed of light in vacuum is:
(A) $\frac{1}{2}$
(B) $\frac{2}{237}$
(C) $\frac{1}{137}$
(D) $\frac{1}{257}$
Multiple Choice
ID- 15366
49. According to Bohr's theory, the wave number of the last line of Balmer series is $(Given\, R = 1.1 × 10^7\, m^{-1})$
(A) $5.5 × 10^5\, m^{-1}$
(B) $4.4 × 10^7\, m^{-1}$
(C) $2.75 × 10^6\, m^{-1}$
(D) $2.75 × 10^8\, m^{-1}$
Multiple Choice
ID- 15367
50. What is the ratio of the shortest wavelength of the Balmer series to the shortest wavelength of the Lyman series?
(A) 4 : 1
(B) 4 : 3
(C) 4 : 9
(D) 5 : 9
Multiple Choice
ID- 15368
51. The de-Broglie wavelength of an electron in the first Bohr's orbit is:
(A) equal to one-fourth the circumference of the first orbit
(B) equal to half the circumference of the first orbit
(C) equal to twice the circumference of the first orbit
(D) equal to the circumference of the first orbit
Multiple Choice
ID- 15369
52. The excitation energy of Lyman last line is:
(A) the same as ionisation energy
(B) the same as the last absorption line in Lyman series
(C) both A and B
(D) different from A and B
Multiple Choice
ID- 15370
53. If the wavelength of the first line of the Balmer series of hydrogen is 6561 Å, the wavelength of the second line of the series should be:
(A) 13122 Å
(B) 3280 Å
(C) 4860 Å
(D) 2187 Å
Multiple Choice
ID- 15371
54. Bohr's basic idea of discrete energy levels in atoms and the process of emission of protons from the higher levels to lower levels was experimentally confirmed by experiments performed by:
(A) Michelson-Morley
(B) Millikan
(C) Joule
(D) Franck and Hertz
Multiple Choice
ID- 15372
55. An atom stays in an excited state for about:
(A) 10 micro seconds
(B) 10 milli seconds
(C) 10 nano seconds
(D) 10 seconds
Multiple Choice
ID- 15373
56. The energy equivalent to one atomic mass unit is:
(A) $1.6 × 10^{-19}\, J$
(B) $6.02 × 10^{23}\, J$
(C) $9.31\, MeV$
(D) $931\, MeV$
Multiple Choice
ID- 15374
57. Who explained the splitting of special lines in magnetic field?
(A) Zeeman
(B) Bohr
(C) Summerfield
(D) Einstein
Multiple Choice
ID- 15375
58. The mass of a neutron is:
(A) $1.00866\, u$
(B) $1.0866\, u$
(C) $1.866\, u$
(D) $0.1866\, u$
Multiple Choice
ID- 15376
59. Isobars have the same:
(A) $A$
(B) $Z$
(C) $N$
(D) All of these
Multiple Choice
ID- 15377
60. Isotones have the same:
(A) $A$
(B) $Z$
(C) $N$
(D) None of these
Multiple Choice
ID- 15378
61. Half-life of a substance depends on:
(A) pressure
(B) temperature
(C) density
(D) None of these
Multiple Choice
ID- 15379
62. The concept of electron spin was introduced by:
(A) Becquerel
(B) Goudsmit
(C) Millikan
(D) Uhlenbeck and Goudsmit
Multiple Choice
ID- 15380
63. The principal that a quantum orbital cannot be occupied by more than two electrons was given by:
(A) Pauli
(B) Millikan
(C) Hund
(D) None of these
Multiple Choice
ID- 15381
64. For ionization of excited Hydrogen atom, the required energy is:
(A) a little less than 13.6
(B) equal to 13.6
(C) more than 13.6
(D) 3.4 or less
Multiple Choice
ID- 15382
65. Artificial radioactivity was discovered by:
(A) Joliot
(B) Becquerel
(C) Pauli
(D) None of these
Multiple Choice
ID- 15383
66. β -decay produces:
(A) isobars
(B) isotopes
(C) isotones
(D) None of these
Multiple Choice
ID- 15384
67. Natural radioactivity was discovered by:
(A) Joliot
(B) Becquerel
(C) Pauli
(D) None of these
Multiple Choice
ID- 15385
68. Transmutation of nuclei was discovered by:
(A) Rutherford
(B) Becquerel
(C) Pauli
(D) None of these
Multiple Choice
ID- 15386
69. The energy equivalent to mass defect is called:
(A) binding energy
(B) internal energy
(C) external energy
(D) enthalpy
Multiple Choice
ID- 15387
70. The total energy that will be released if a nucleus is built from its constituents is called the:
(A) binding energy of the nucleus
(B) binding energy of the solid
(C) binding energy of the atom
(D) None of these
Multiple Choice
ID- 15388
71. The binding energy of $^4_2He$ is about:
(A) $28.3\, eV$
(B) $28.3\, MeV$
(C) $28.3\, J$
(D) $2.83\, MeV$
Multiple Choice
ID- 15389
72. If the atom $^{257}_{100}Fm$ follows Bohr model and the radius of this atom is $n$ times Bohr radius, then $n$ will be:
(A) $100$
(B) $200$
(C) $4$4
(D) $\frac{1}{100}$
Multiple Choice
ID- 15390
73. For Hydrogen atom, the ratio of energy in its first to second excited state is:
(A) $\frac{1}{4}$
(B) $\frac{2}{3}$
(C) $\frac{4}{9}$
(D) $\frac{4}{1}$
Multiple Choice
ID- 15391
74. The shortest wavelength of $X$-rays emitted from an $X$-ray tube depend on the:
(A) current in the tube
(B) voltage applied to the tube
(C) nature of the gas in the tube
(D) atomic number of target material
Multiple Choice
ID- 15392
75. The speed of an electron in the orbit of hydrogen atom in ground state is:
(A) $C$
(B) $\frac{C}{2}$
(C) $\frac{C}{10}$
(D) $\frac{C}{137}$
Multiple Choice
ID- 15393
76. The unit is defined as $\frac{1}{12}$ of the mass of a carbon-12 atom and is symbolised as $u$. $$1\,u = \frac{\text{mass of carbon - 12 atom}}{12}$$ $1\,u$ is equal to:
(A) $1.66 × 10^{-27}\, kg$
(B) $1.66 × 10^{-24}\, kg$
(C) $1.66 × 10^{-22}\, kg$
(D) None of these
Multiple Choice
ID- 15394
77. Who discovered the positron?
(A) Chadwick
(B) Bohr
(C) Maxwell
(D) Anderson
Multiple Choice
ID- 15395
78. The mass of proton is about:
(A) $9.11 × 10^{-31}\, kg$
(B) $9.11 × 10^{-30}\, kg$
(C) $1.66 × 10^{-27}\, kg$
(D) $1\, kg$
Multiple Choice
ID- 15396
79. How many electrons are contained in $^{238}_{92}U$ nucleus?
(A) 92
(B) 146
(C) 238
(D) 0
Multiple Choice
ID- 15397
80. Chadwick was awarded the Nobel prize in Physics in 1935 for his discovery of:
(A) electron
(B) proton
(C) neutron
(D) None of these
Multiple Choice
ID- 15398
81. The density of a nucleus is of the order of:
(A) $10^{15}\, kg\, m^{-3}$
(B) $10^{18}\, kg\, m^{-3}$
(C) $10^{17}\, kg\, m^{-3}$
(D) $10^{16}\, kg\, m^{-3}$
Multiple Choice
ID- 15399
82. In the given reaction: $$^{A}_{Z}X \rightarrow\, ^{A}_{Z+1}Y \rightarrow\, ^{A-4}_{Z-1}K \rightarrow\, ^{A-4}_{Z-1}K$$ radioactive radiations are emitted in the sequence:
(A) α, β, γ
(B) β, α, γ
(C) γ, α, β
(D) β, γ, α
Multiple Choice
ID- 15400
83. When the mass of a sample of a radioactive substance decreases, the mean life of the sample:
(A) increases
(B) decreases
(C) remain unchanged
(D) first decreases then increases
Multiple Choice
ID- 15401
84. Alpha particle emitted from a radioactive material are:
(A) Helium nuclei
(B) Hydrogen nuclei
(C) Lithium nuclei
(D) None of the above
Multiple Choice
ID- 15402
85. The half life of a radioactive decay is $n$ times its mean life, $n$ is equal to:
(A) $0.6930$
(B) $0.0693$
(C) $\frac{1}{0.6930}$
(D) $0.3070$
Multiple Choice
ID- 15403
86. Rutherford is the unit of:
(A) radioactivity
(B) energy
(C) photoelectric current
(D) magnetic field
Multiple Choice
ID- 15404
87. According to Yukawa's theory of nuclear forces, the origin of nuclear force between nucleons is due to the exchange of:
(A) measons
(B) photons
(C) electrons
(D) positrons
Multiple Choice
ID- 15405
88. An electron and a positron each having a mass equivalent to $0.53\, MeV$ annihilate each other and produce a photon. The minimum energy of the photon is:
(A) $0.53\, MeV$
(B) $1.06\, MeV$
(C) $2.12\, MeV$
(D) $zero$
Multiple Choice
ID- 15406
89. The wavelength of $γ$-rays is of the order of:
(A) $10^{-8}$
(B) $10^{-5}$
(C) $10^{-11}$
(D) $10^{-22}$
Multiple Choice
ID- 15407
90. Radius of $1^{st}$ Bohr orbit is $a_0$ (= 0.529Å). What is the radius of $2^{nd}$ Bohr orbit?
(A) $8a_0$
(B) $2a_0$
(C) $4a_0$
(D) $2\sqrt{2}a_0$
Multiple Choice
ID- 15408
BSEB, 2016 (C)
91. Which series of hydrogen spectrum does not lie in infrared region?
(A) Humphreys series
(B) Pfund series
(C) Bracket series
(D) Lyman series
Multiple Choice
ID- 15409
BSEB, 2016 (C)
92. The energy of electron in the first Bohr orbit of hydrogen atom is $-13.6\, eV$. What is energy of electron in its $2^{nd}$ Bohr orbit?
(A) $-3.4\, eV$
(B) $-6.8\, eV$
(C) $-27.2\, eV$
(D) $+3.4\, eV$
Multiple Choice
ID- 15410
BSEB, 2017 (C)
93. Full wave reftifer uses:
(A) two diodes
(B) three diodes
(C) four diodes
(D) five diodes
Multiple Choice
ID- 15411
BSEB, 2018 (A)
94. The atomic number and mass number for a specimen are $Z$ and $A$ respectively. The number of neutrons in the atom will be:
(A) $A$
(B) $Z$
(C) $A+Z$
(D) $A-Z$
Multiple Choice
ID- 15416
BSEB, 2016 (C), 2019 (C)
95. Which of the following has maximum penetrating power?