NCERT Class 12 MCQ Quiz Hub

1. How many electrons are contained in 23892U nucleus?
92
146
238
0

2. Chadwick was awarded the Nobel prize in Physics in 1935 for his discovery of:
electron
proton
neutron
None of the above

3. The density of a nucleus is of the order of:
1015 kg m-3
1018 kg m-3
1017 kg m-3
1016 kg m-3

4. When the mass of a sample of a radioactive substance decreases, the mean life of the sample:
increases
decreases
remain unchanged
first decreases then increases

5. Alpha particle emitted from a radioactive material are:
Helium nuclei
Hydrogen nuclei
Lithium nuclei
None of the above

6. The half life of a radioactive decay is n times its mean life, n is equal to:
0.6930
0.0693
10.6930
0.3070

7. Rutherford is the unit of:
radioactivity
energy
photoelectric current
magnetic field

8. According to Yukawa’s theory of nuclear forces, the origin of nuclear force between nucleons is due to the exchange of
mesons
photons
electrons
positrons

9. 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.
0.53 MeV
1.06 MeV
2.12 MeV
zero

10. The ground state energy of Hydrogen atom is -13.6 eV. What is the potential energy of electron in this state?
0 eV
-13.6 eV
2 eV
-27.2 eV

11. The Bohr model of atom:
assumes that the angular momentum of electron is quantized
uses Einstein’s photoelectric equation
predicts continuous emission spectra for atoms
predicts the same emission spectra for all types of atoms

12. Nuclear force is:
strong, short range and charge independent force
charge independent, attractive and long range force
strong, charge dependent and short range attractive force
long range, change dependent and attractive force

13. If radio active nuclei emits β-particle, then mass-number:
increased by 1 unit
decreases by 1 unit
increases by 2 unit
decreases by 2 unit

14. An alpha particle is emitted from 88Ra226, then the product nuclei has:
Z = 84, A = 224
Z = 86, A = 224
Z = 86, A = 222
Z = 82, A = 222

15. X-ray was discovered by :
Becqueral
Marie curie
Roengton
Vanlaw

16. Fusion takes place at high temperature because:
Atom are ionised at high temperature
Molecules break up at high temperature
Nuclei break up at high temp.
Kinetic energy is high enough to overcome repulsion between nuclei

17. What percentage of radioactive substance is left after 5 half lives?
3.125%
6.25%
.33%
31%

18. The helium atom does not contain
two protons
two electrons
two neutrons
six nucleons

19. The more readily fissionable isotope of uranium has an atomic mass of:
234
235
236
238

20. Energy of electron in the 1st orbit of H-atom is:
-13.6 MeV
-13.6 eV
-13.6 J
13.6 J

21. The mass no. of a nucleus is M and its atomic no. is Z. The number of neutrons in the nucleus is :
M – Z
M
Z
M + Z

22. The phenomena of radioactivity is:
Exothermic change with increase or decrease with temperature
increases on applied pressure
nuclear process does not depend on external factors
None of the above