**Atomic Physics MCQ with Answers**

**Q1. let T _{g} and T_{e} be the kinetic energies of the electron in the ground and the third excited states of a hydrogen atom, respectively. According to the Bohr model, the ratio T_{g}/T_{e} is**

(a) 3

(b) 4

(c) 9

(d) 16

**Q2. Given that the ionization energies of Hydrogen ( ^{1}H) and (^{3}Li) are 13.6 eV and 5.39 eV, respectively, the effective nuclear charge experienced by the valence electron of ^{3}Li atom may be estimated in terms of the proton charge e as**

(a) 0.63 e

(b) 1.26 e

(c) 1.59 e

(d) 3.00 e

**Q3. Consider the high excited states of a Hydrogen atom corresponding to large values of the principal Quantum number (n >> 1). The wavelength λ of a photon emitted due to an electron undergoing a transition between two such states with consecutive values of n (i.e, ψ _{n+1} → ψ_{n} ) is related to the wavelength λ_{a} of the K_{a} line of Hydrogen by**

(a) λ = n^{3} λ_{a} / 8

(b) λ = 3n^{3} λ_{a} / 8

(c) λ = n^{2} λ_{a}

(d) λ = 4λ_{a} /_{n2}

**Q4. The velocity of an electron in the ground state of a hydrogen atom is v _{H} . If v_{p} be the velocity of an electron in the ground state of positronium , then**

(a) v_{p} = v_{H}

(b) v_{p} = 2v_{H}

(c) v_{p} = v_{H}/2

(d) v_{p} = √2 v_{H}

**Q5. A sample of ordinary hydrogen ( _{1}H^{1}) gas in a discharge tube was seen to emit the usual Balmer Spectrum. On careful examination , however, it was found that the H_{a} line in the spectrum was split into two fine lines, one an intense line at 656.28 nm, and the other a faint line at 656.04 nm. From this, one can conclude that the gas sample has a small impurity of**

(a) _{1}H^{2}

(b) _{1}H^{3}

(c) _{2}He^{4}

(d) H_{2}O

**Q6. The binding energy of the hydrogen atom (electron bound to proton) is 13.6 eV. The binding energy of positronium (electron bound to positron) is**

(a) ^{13.6}/_{180} eV

(b) ^{13.6}/_{2} eV

(c) 13.6 × 1810 eV

(d) 13.6 × 2 eV

**Q7. If a proton were ten times lighter, then the ground state energy of the electron in a Hydrogen atom would have been**

(a) Less

(b) More

(c) The same

(d) Depends on the electron mass

**Q8. If the Rydberg constant of an atom of finite mass is αR _{∞} , where R_{∞} is the Rydberg constant corresponding to an infinite nuclear mass, the ratio of the electronic to nuclear mass of the atom is :**

(a) ^{(1 – α)}/_{α}

(b) ^{(α – 1)}/_{α}

(c) (1 – α)

(d) ^{1}/_{α}

**Q9. The wavelength of one of the visible lines in the spectrum of the hydrogen atom is approximately 6560 Å . It is known that this corresponds to a transition between the states with the principal quantum number n = 2 and n = 3. What will be the frequency corresponding to the transition from the ground state to the first excited state **

(a) 4.56 × 10^{14} Hz

(b) 1.65 × 10^{15} Hz

(c) 2.47 × 10^{15} Hz

(d) 3.29 × 10^{15} Hz

**Q10. An X-ray machine operates at a potential of 5000 V. What is the minimum possible value of wavelength present in the radiations ?**

(a) 0.0124 nm

(b) 0.0245 nm

(c) 0.124 nm

(d) 0.248 nm

**Q11. Consider the simple Bohr model of the Hydrogen atom . Its ground state has an energy of – 13.6 eV. The wavelength of the Electromagnetic radiation emitted when the atom makes a transition from first excited state to the ground state is **

(a) 1.22 × 10^{-5} cm

(b) 2.44 × 10^{-5} cm

(c) 6.22 × 10^{-5} cm

(d) 4.32 × 10^{-5} cm

**Q12. The first ionization potential of helium atom is 24.6 eV . What is the minimum energy required to remove both the electrons of a neutral helium atom ?**

(a) 108.8 eV

(b) 79.0 eV

(c) 49.2 eV

(d) 37.9 eV

**Q13. A three-level system of atom has N _{1} atoms in level E_{1} ,N_{2} in Level E_{2} and N_{3} in Level E_{3} (N_{2} > N_{1} > N_{3}) and (E_{1} < E_{2} < E_{3}) . Laser emission is possible for the transitions :**

(a) E_{2} → E_{1}

(b) E_{3} → E_{2}

(c) E_{2} → E_{3}

(d) E_{3} → E_{1}

**Q14. Assuming LS coupling, the lowest energy level for carbon (Z=6) is **

(a) ^{1}S_{0}

(b) ^{3}P_{0}

(c) ^{1}D_{2}

(d) ^{1}S_{1}

**Q15. Splitting of Spectral lines in the Stark Effect depends on :**

(a) Magnetic Quantum Number

(b) Spin Quantum Number

(c) Azimuthal Quantum Number

(d) Principal Quantum Number

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*Answer Key* (if you find any answer wrong, feel free to Correct us)

*Answer Key*

01. | (d) | 06. | (a) | 11. | (a) |

02. | (b) | 07. | (b) | 12. | (b) |

03. | (b) | 08. | (a) | 13. | (a) |

04. | (a) | 09. | (c) | 14. | (b) |

05. | (b) | 10. | (d) | 15. | (a) |