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12th Standard Physics Atomic and Nuclear physics English Medium Free Online Test One Mark questions 2020 - 2021

12th Standard

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Physics

Time : 00:20:00 Hrs
Total Marks : 20
    Answer all the questions
    20 x 1 = 20
  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 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

  3. If the nuclear radius of 27Al is 3.6 fermi, the approximate nuclear radius of 64Cu, in femi is _____.

    (a)

    2:4

    (b)

    1.2

    (c)

    4.8

    (d)

    3.6

  4. A radioactive nucleus (initial mass number A and atomic number Z) emits two α-particles and 2 positons. The ratio of number of neutrons to that of proton in the final nucleus will be _____.

    (a)

    \(\frac{A-Z-4}{Z-2}\)

    (b)

    \(\frac{A-Z-2}{Z-6}\)

    (c)

    \(\frac{A-Z-4}{Z-6}\)

    (d)

    \(\frac{A-Z-12}{Z-4}\)

  5. A radiative element has N0 number of nuclei at t = 0. The number of nuclei remaining after half of a half-life _____.(that is, at time t = \(\frac{1}{2}T_\frac{1}{2}\))

    (a)

    \(\frac{N_0}{2}\)

    (b)

    \(\frac{N_0}{\sqrt2}\)

    (c)

    \(\frac{N_0}{4}\)

    (d)

    \(\frac{N_0}{8}\)

  6. Bohr's postulate is based on _______________.

    (a)

    conservation of linear momentum

    (b)

    quantisation of angular momentum

    (c)

    conservation of quantum frequency

    (d)

    none of these

  7. 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

  8. An alpha nucleus of energy 1/2 mv2 bombards a heavy nuclear target of charge Ze. Then the distance of the closest approach for the alpha nucleus will be proportional to ____________.

    (a)

    v2

    (b)

    \(\frac{1}{m}\)

    (c)

    \(\frac{1}{v^$}\)

    (d)

    \(\frac{1}{Ze}\)

  9. The fig. represents the observed intensity of X-rays emitted by an X-ray tube as a function of wavelength. The sharp peaks A and B denote ____________.
     

    (a)

    continuous spectrum

    (b)

    band spectrum

    (c)

    characteristic spectrum

    (d)

    white radiations

  10. A beam of electron posses undeflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off and the same magnetic field is maintained, the electrons move ______________.

    (a)

    in a circular orbit

    (b)

    along a parabolic path

    (c)

    along a straight line

    (d)

    in an elliptical orbit

  11. For first-order X-ray diffraction, the wavelength in of the X-ray is equal to the lattice spacing at a glancing angle is _____________.

    (a)

    15°

    (b)

    60°

    (c)

    45°

    (d)

    30°

  12. In the given nuclear fission reaction, 'X' denotes which particle?
    92U235 + 0n1 56Ba141 + 36Kr92 + 3X + Q

    (a)

    electron

    (b)

    α -particle

    (c)

    neutron

    (d)

    neutrino

  13. Elements having atomic number greater than ______ are radioactive.

    (a)

    48

    (b)

    68

    (c)

    88

    (d)

    83

  14. Gamma rays are extensively used to destroy __________ affected cells

    (a)

    Sickle-cell anaemia

    (b)

    Cancer

    (c)

    HIV

    (d)

    Polio virus

  15. Irene Curie and F. Joliot discovered ______ in the year 1934.

    (a)

    natural radioactivity

    (b)

    fluorescence

    (c)

    artificial radioactivity

    (d)

    hydrogen bomb

  16. Minimum size of a system in which at least 1 neutron is available for further fission is called __________

    (a)

    cut-off size

    (b)

    critical size

    (c)

    range of reactor

    (d)

    capability criteria

  17. Pressurised heavy-water reactors in our country generally use _____ as fuel.

    (a)

    natural uranium oxide

    (b)

    radioactive phosphorous

    (c)

    titanium dioxide

    (d)

    plutonium

  18. Graphite is used as a __________ in nuclear reactors.

    (a)

    moderator

    (b)

    coolant

    (c)

    detector

    (d)

    fuel

  19. In a nuclear reactor, cadmium rods are used to _____________

    (a)

    speed up neutrons

    (b)

    slow down neutrons

    (c)

    absorb neutrons

    (d)

    remove heat

  20. 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

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