12th physics chapter 12: full solution, notes, MCQ, & free PDF | Bihar board

1. The first model of atom in 1898 was proposed by

• • (a) Ernst Rutherford
  • (b) Albert Einstein
  • (c) J.J. Thomson
  • (d) Niels Bohr

Answer: (c) J.J. Thomson

2. In Geiger-Marsden scattering experiment, the trajectory traced by an a-particle depends on

• • (a) number of collision
  • (b) number of scattered a-particles
  • (c) impact parameter
  • (d) none of these

Answer: (c) impact parameter

3. 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°

Answer: (a) 0° and 180°

4. In the Geiger-Marsden scattering experiment, is case of head-on collision the impact parameter should be

• • (a) maximum
  • (b) minimum
  • (c) infinite
  • (d) zero

Answer: (a) maximum

5. Rutherford’s experiments suggested that the size of the nucleus is about

• • (a) 10^-14 m to 10^-12 m
  • (b) 10^-15 m to 10^-13 m
  • (c) 10^-15 m to 10^-14 m
  • (d) 10^-15 m to 10^-12 m

Answer: (c) 10^-15 m to 10^-14 m

6. Which of the following spectral series falls within the visible range of electromagnetic radiation?

• • (a) Lyman series
  • (b) Balmer series
  • (c) Paschen seriee
  • (d) Pfund series

Answer: (b) Balmer series

7. The first spectral series was discovered by

• • (a) Balmer
  • (b) Lyman
  • (c) Paschen
  • (d) Pfund

Answer: (a) Balmer

8. Which of the following postulates of the Bohr model led to the quantization of energy of the hydrogen atom?

• • (a) The electron goes around the nucleus in circular orbits.
  • (b) The angular momentum of the electron can only be an integral multiple of h/2π.
  • (c) The magnitude of the linear momentum of the electron is quantized.
  • (d) Quantization of energy is itself a postulate of the Bohr model.

Answer: (b) The angular momentum of the electron can only be an integral multiple of h/2π.

9. The Bohr model of atoms

• • (a) assumes that the angular momentum of elec-trons is quantized.
  • (b) uses Einstein’s photoelectric equation.
  • (c) predicts continuous emission spectra for at-oms.
  • (d) predicts the same emission spectra for all types of atoms.

Answer: (a) assumes that the angular momentum of elec-trons is quantized.

10. The Bohr model of atoms : 

• • (A) assumes that the angular momentum of electrons is quantized
  • (B) uses Einstein’s photoelectric equation
  • (C) predicts continuous emission spectra for atoms
  • (D) predicts the same emission spectra for all types of atoms

Answer: (A) assumes that the angular momentum of electrons is quantized

bseb most important notes 12th physics chapter 12 

11. Who explained the splitting of special lines in magnetic field ?

• • (A) Zeeman
  • (B) Bohr
  • (C) Summerfield
  • (D) Einstein

Answer: (A) Zeeman 

12. The mass of a neutron is : 

• • (A) 1.00866 u
  • (B) 1.0866 u
  • (C) 1.866 u
  • (D) 0.1866 u

Answer: (A) 1.00866 u 

13. Half-life of a substance depends on: 

• • (A) pressure
  • (B) temperature
  • (C) density
  • (D) None of these

Answer: (D) None of these

14. The concept of electron spin was introduced by :

• • (A) Becquerel
  • (B) Goudsmit
  • (C) Millikan
  • (D) Uhlenbeck and Goudsmith

Answer: (D) Uhlenbeck and Goudsmith 

15. β-decay produces : 

• • (A) isobars
  • (B) isotopes
  • (C) isotones
  • (D) All the above

Answer: (A) isobars 

16. Transmutation of nuclei was discovered by : 

• • (A) Rutherford
  • (B) Becquerel
  • (C) Pauli
  • (D) None of these

Answer: (A) Rutherford 

17. The energy equivalent to mass defect is called : 

• • (A) binding energy
  • (B) internal energy
  • (C) external energy
  • (R) enthalpy

Answer: (A) binding energy

18. The binding energy of He is about : 

• • (A) 28.3 eV
  • (B) 28.3 Mev
  • (C) 28.3 J
  • (D) 2.83 Mev
  •  

Answer: (B) 28.3 Mev

19. The binding energy of a deuteron is about : 

• • (A) 2.22 MeV
  • (B) 2.22 J
  • (C) 2.22 eV
  • (D) None of these

Answer: (A) 2.22 MeV 

bihar board most mcq solution 12th physics chapter 12

20. Who discovered the positron ? 

• • (A) Chadwick
  • (B) Bohr
  • (C) Maxwell
  • (D) Anderson

Answer: (D) Anderson

21. The mass of proton is about : 

• • (A) 9.11 x 10^-31 kg
  • (B) 9.11 x 10^-30 kg .
  • (C) 1.66 x 10^-27 kg
  • (D) 1 kg

Answer: (C) 1.66 x 10^-27 kg

22. Chadwick was awarded the Nobel Prize in Physics in 1935 for his discovery of :

• • (A) electron
  • (B) proton
  • (C) neutron
  • (D) None of these

Answer: (C) neutron 

23. The half life of a radioactive decay is n times its mean life, n is equal to : 

• • (A) 0.6930
  • (B) 0.0693
  • (C) 1 / 0.6930
  • (D) 0.3070

Answer: (A) 0.6930 

24. Rutherford is the unit of: 

• • (A) radioactivity
  • (B) energy
  • (C) photoelectric current
  • (D) magnetic field

Answer: (A) radioactivity

25. The wavelength of Y -rays is of the order of: 

• • (A) 10^-8 m
  • (B) 10^-5 me
  • (C) 10^-11 m
  • (D) 10^-22 m

Answer: (C) 10^-11 m 

26. Which series of hydrogen spectrum does not lie in infrared region? 

• • (A) Humphreys series
  • (B) Pfund series
  • (C) Bracket series
  • (D) Lyman series

Answer: (D) Lyman series

27. The energy of electron in first Bohr orbit of hydrogen atom is -13.6 eV. What is energy of electron in its 2nd Both-orbit. 

• • (A) – 3.4 eV
  • (B) – 6.8 eV
  • (C) – 27.2 eV,
  • (D) + 3.4 eV

Answer: (A) – 3.4 eV 

28. Full wave rectifier uses : 

• • (A) two diodes
  • (B) three diodes
  • (C) four diodes
  • (D) five diodes

Answer: (A) two diodes 

29. 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

Answer: (D) A-Z 

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