Page 1 CBSE TEST PAPER-02 CLASS - XII PHYSICS (Atoms and Nuclei) 1. Complete the following nuclear reactions [1] (a) 9 1 6 1 3 4 ....................... Be H Li + ? + (b) 4 10 13 5 2 7 ..................... B He N + ? + 2. What is value ? - of a nuclear reaction? [1] 3. What fraction of tritium will remain after 25 years? Given half life of tritium as 12.5 years [1] 4. Calculate the kinetic energy and potential energy of an electron in the first orbit of hydrogen atom. Given e = 1.6 × 10 -19 C and r = 0.53 × 10 -10 m. [2] 5. A neutron is absorbed by a 3 Li nucleus with subsequent emission of alpha particle. Write the corresponding nuclear reaction? [2] 6. If the activity of a radioactive substance drops to 1 8 th of its initial value in 30 years, find its half life period? [2] 7. Show that nuclear density is in dependent of mass number A of a nucleus? [2] 8. The wavelength of the first member of Balmer series in the hydrogen spectrum is 6563A o . Calculate the wavelength of the first member of lyman series in the same spectrum. [3] 9. A neutron is absorbed by a 6 3Li nucleus with subsequent emission of . particle a - Write the corresponding nuclear reaction. Calculate the energy released in this reaction. [3] Given mass of 6 3Li = 6.015126 a.m.u. Mass of 4 2 He = 4.000 26044 a.m.u. Mass of neutron 1 o n ? ? ? ? ? ? = 1.0086654 a.m.u. Mass of tritium 1 1 H ? ? ? ? ? ? = 3.016049 a.m.u. 10. Define decay constant of a radioactive sample. Which of the following radiation a-rays, ß-rays and ?-rays. (i) Are similar to X – rays? (ii) Are easily absorbed by matter? [3]Read More

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