12th Physics Question

12th Exam Physics VVI Objective Atoms Chapter Important Question


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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