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12th Physics - Atomic and Nuclear Physics Model Question Paper

Atomic and Nuclear Physics Model Question Paper

12th Standard

    Reg.No. :
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Physics

Time : 01:00:00 Hrs
Total Marks : 40
    5 x 1 = 5

  1. The electric potential of an electron is given by \(V={ V }_{ 0 } \ In\left( \frac { r }{ { r }_{ 0 } } \right) \), where r0 is a constant. If Bohr atom model is valid, then variation of radius of nth orbit rn with the principal quantum number n is _____.

    (a)

    \({ r }_{ n }∝ \frac { 1 }{ n } \)

    (b)

    \({ r }_{ n }∝ n\)

    (c)

    \({ r }_{ n }∝\frac { 1 }{ { n }^{ 2 } } \)

    (d)

    \({ r }_{ n }∝ { n }^{ 2 }\)

  2. 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)

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

  3. The half-life period of a radioactive element A is same as the mean life time of another radioactive element B. Initially both have the same number of atoms. Then _____.

    (a)

    A and B have the same decay rate initially

    (b)

    A and B decay at the same rate always

    (c)

    B will decay at faster rate than A

    (d)

    A will decay at faster rate than B

  4. The ionization energy of hydrogen atom is -13.6e V. The energy corresponding to a transition between 3rd and 4th orbit is ______________.

    (a)

    3.40 eV

    (b)

    1.51 eV

    (c)

    0.85 eV

    (d)

    0.66 eV

  5. The total energy of electrons in the ground state of a hydrogen atom is -13.6 eV. The k.E of an electron in the first excited state is ____________.

    (a)

    6.8 eV

    (b)

    13.6 eV

    (c)

    1.7 eV

    (d)

    3.4 eV

    6. 5 x 2 = 10

  6. What is isotope? Give an example.

  7. Define atomic mass unit u.

  8. What is mass defect?

  9. Why neutrons in the nucleus are stable?

  10. What causes the sun to expand?

    11. 5 x 3 = 15

  11. Discuss the properties of neutrino and its role in beta decay.

  12. Discuss the process of nuclear fission and its properties.

  13. Explain in detail the four fundamental forces in nature.

  14. With respect to power generation, what are the relative advantages and disadvantages of fusion type and Fission type reactors?

  15. What are radioactive elements? What are the factors that affect radio activity?

    16. 2 x 5 = 10

  16. Calculate the radius of the earth if the density of the earth is equal to the density of the nucleus.[mass of earth 5.97 x 1024 kg].

  17. Calculate the number of nuclei of carbon-14 undecayed after 22,920 years if the initial number of carbon-14 atoms is 10,000. The half-life of carbon-14 is 5730 years.

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