12th Exam Physics VVI Objective Atoms Chapter Important Question
ATOMS
1. Cathode rays are :
(A) electrons
(B) neutrons
(C) protons
(D) photons
| Answer:- A |
2. γ-rays are similar to :
(A) C-rays
(B) B-rays
(C) cathode rays
(D) X-rays
| Answer:- D |
3. β-rays are fast moving :
(A) photons
(B) protons
(C) electrons
(D) neutrons
| Answer:- C |
4. Which of the following series of hydrogen spectrum is in visible range ?
(A) Lyman series
(B) Balmer se
(C) Paaschen series
(D) Brackett series.
| Answer:- B |
5. Electron-volt (eV) is the measure of:
(A) charge
(B) potential difference
(C) current
(D) energy
| Answer:- D |
6. The specific charge of electron is :
(A) 1.8 x 1011 c/kg
(B) 1.8 x 10-19 c/kg
(C) 1.9 x 10-19 c/kg
(D) None of these
| Answer:- A |
7. The number of neutrons in an atom of 90Th230 is :
(A) 90
(B) 140
(C) 230
(D) 320
| Answer:- B |
8. 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 |
9. 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. 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 |
11. Who explained the splitting of special lines in magnetic field ?
(A) Zeeman
(B) Bohr
(C) Summerfield
(D) Einstein
| Answer:- A |
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 |
13. Half-life of a substance depends on:
(A) pressure
(B) temperature
(C) density
(D) None of these
| Answer:- D |
14. The concept of electron spin was introduced by :.
(A) Becquerel
(B) Goudsmit
(C) Millikan
(D) Uhlenbeck and Goudsmit
| Answer:- D |
15. β-decay produces :
(A) isobars
(B) isotopes
(C) isotones
(D) All the above
| Answer:- A |
16. Transmutation of nuclei was discovered by :
(A) Rutherford
(B) Becquerel
(C) Pauli
(D) None of these
| Answer:- A |
17. The energy equivalent to mass defect is called :
(A) binding energy
(B) internal energy
(C) external energy
(R) enthalpy
| Answer:- A |
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 |
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 |
20. Who discovered the positron ?
(A) Chadwick
(B) Bohr
(C) Maxwell
(D) Anderson
| Answer:- D |
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 |
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 |
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 |
24. Rutherford is the unit of:
(A) radioactivity
(B) energy
(C) photoelectric current
(D) magnetic field
| Answer:- A |
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 |
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 |
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 |
28. Full wave rectifier uses :
(A) two diodes
(B) three diodes
(C) four diodes
(D) five diodes
| Answer:- A |
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 |
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