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Atomic and Nuclear Physics Practice Question Paper

12th Standard

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Physics

Time : 01:00:00 Hrs
Total Marks : 50
    8 x 1 = 8
  1. Suppose an alpha particle accelerated by a potential of V volt is allowed to collide with a nucleus of atomic number Z, then the distance of closest approach of alpha particle to the nucleus is _____.

    (a)

    \(14.4\frac { Z }{ V } \mathring { A } \)

    (b)

    \(14.4\frac { V }{ Z } \mathring { A } \)

    (c)

    \(1.44\frac { Z }{ V } \mathring { A } \)

    (d)

    \(1.44\frac { V }{ Z } \mathring { A } \)

  2. The charge of cathode rays particle is _____.

    (a)

    Positive

    (b)

    negative

    (c)

    neutral

    (d)

    not defined

  3. In J.J. Thomson e/m experiment, electrons are accelerated through 2.6 kV enter the region of crossed electric field and magnetic field of strength 3.0 x 104 Vm-1 and 1.0 x 10-3 T, respectively, and pass through it and undeflected, then the specific charge is _____.

    (a)

    1.6 × 1010 C kg–1

    (b)

    1.7 × 1011 Ckg–1

    (c)

    1.5 × 1011 Ckg–1

    (d)

    1.8 × 1011 Ckg–1

  4. The ratio of the wavelengths radiation emitted for the transition from n = 2 to n = 1 in Li++, He+ and H is _____.

    (a)

    1:2:3

    (b)

    1:4:9

    (c)

    3:2:1

    (d)

    4:9:36

  5. The ground state energy of a hydrogen atom is 13.6 eV. The energy needed to ionize H2 atom from its second excited state ______________.

    (a)

    1.51 eV

    (b)

    3.4 eV

    (c)

    13.6 eV

    (d)

    none

  6. The energy of the ground state of hydrogen is -13.6 eV. The energy of the first excited state is _____________.

    (a)

    -27.2 eV

    (b)

    -52.4 eV

    (c)

    -3.4 eV

    (d)

    -6.8 eV

  7. The explosion of hydrogen bomb is based on the principle of _________________.

    (a)

    uncontrolled fission reaction

    (b)

    nuclear fusion reaction

    (c)

    controlled fission

    (d)

    photo electric effect

  8. 1 Curie is ________________.

    (a)

    activity of 1 g of Uranium

    (b)

    I disintegration / second

    (c)

    3.7 x 1016 becquerel

    (d)

    1.6 x 1012 disintegration / second

  9. 1 x 2 = 2
  10. Assertion: Electrons in the atom are held due to coulomb forces.
    Reason: The atom is stable only because the centripetal force due to coulomb's law is balanced by the centrifugal force.
    Codes:
    (a) Assertion and Reason are correct and Reason is the correct explanation of Assertion.
    (b) Assertion and Reason are true but Reason is the false explanation of the Assertion.
    (c) Assertion is true but Reason is false.
    (d) Assertion is false but Reason is true.

  11. 1 x 2 = 2
  12. (a) Breaking nucleus Nuclear fission
    (b) Slow neutrons 0- 1000 eV
    (c) Fast neutrons 0.5 MeV - 10 MeV
    (d) Nuclear fusion 1.5 x 107 K
  13. 1 x 1 = 1
  14. CHOOSE THE CORRECT STATEMENTS
    (i) Cathode rays produce heat, when allowed to fall on matter.
    (ii) Cathode rays produce X-ray, when allowed to fall on material of high atomic weight.
    (iii) Cathode rays are positively charged particles
    (iv) Cathode ray ionize the gas.
    (a) I, II and III only
    (b) I, II and IV only
    (c) I and II only
    (d) II, III and IV only

  15. 5 x 2 = 10
  16. What are cathode rays?

  17. Write the properties of cathode rays.

  18. Which ray has high ionising power? Why?

  19. What is nuclear chain reaction?

  20. State the reasons. Why a chain reaction stops?

  21. 4 x 3 = 12
  22. Explain the J.J. Thomson experiment to determine the specific charge of electron.

  23. Discuss the Millikan’s oil drop experiment to determine the charge of an electron.

  24. What does a neutron moderator do?

  25. Write the properties of neutrino?

  26. 3 x 5 = 15
  27. Consider two hydrogen atoms HA and HB in ground state. Assume that hydrogen atom HA is at rest and hydrogen atom HB is moving with a speed and make head-on collision with the stationary hydrogen atom HA. After the collision, both of them move together. What is minimum value of the kinetic energy of the moving hydrogen atom HB, such that any one of the hydrogen atoms reaches first excitation state.

  28. In the Bohr atom model, the frequency of transitions is given by the following expression \(v=Rc\left( \frac { 1 }{ { n }^{ 2 } } -\frac { 1 }{ { m }^{ 2 } } \right) \), where n < m, Consider the following transitions:

    Transitions m➝n
    1 3➝2
    2 2➝1
    3 3➝1

    Show that the frequency of these transitions obey sum rule (which is known as Ritz combination principle) 

  29. Explain the results of Rutherford α-particle scattering experiment.

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