» CBSE Physics Atom, Molecule, Nuclei Expected Questions : Unit X : CBSE Sample Question Papers

CBSE Physics Atom, Molecule, Nuclei Expected Questions : Unit X Filed under: Class XII Physics Expected Question Long Answer Questions (5-Marks Questions) 1. A neutron is absorbed by a 3L1 nucleus with subsequent emission of alpha particle. Write the corresponding nuclear reaction. Calculate the energy released in this reaction. Given m (3Li6 ) = 6-015126 amu ; m(2He4) = 4-0026044 amu ; m(0n1) = 1-0086654 amu and m( 1H3) = 3-016049 amu. Answer 2. Explain the term fission, fusion and nuclear reactor. Answer 3. Explain the difference between mean life and half life of a radioactive sample. Calculate the number of disintegrations per second of 1 g of a radioactive sample whose half life is 1.4 X 1016 s. The mass number of the sample is 238. Answer 4. Describe Rutherford’s atomic model. Answer 5. Establish the formula 1 1 1/λ= R [— — — ] for hydrogen atom. n12 n22 Answer 6. Electrons in hydrogen like atom with Z = 3 moles transition from fourth to third orbit. The ;Hi:N photons so emitted are allowed to fall normally on a metal surface to cause photoelectric emission. Determine the work function of the metal if stopping potential tor the most energic photoelectron is 3.95 V and Rydberg’s formula for hydrogen like atom is given to be 1 1 1/λ= RZ2 [— — — ] . n12 n22 Answer 7. A beam of alpha particles and of protons of same velocity v, enter a uniform magnetic field at right angles to the field lines. The particles describe circular orbits. What is the ratio of the radii of these two circles ? Answer Pages: 1 2 3

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