CBSE TEST PAPER-01

CLASS - XII PHYSICS (Atoms and Nuclei)

1. Name the series of hydrogen spectrum lying in ultraviolet and visible region? [1]

2. What is Bohr’s quantisation condition for the angular momentum of an electron in the second orbit? [1]

3. Define Bohr’s radius? [1]

4. State the limitations of Bohis atomic model? [2]

5. The half life period of a radioactive substance is 30 days. What is the time for 34th of its original mass to disintegrate? [2]

6. How many α and β-particles are emitted when 232, 90 Th changes to 208 ,82 Pb [2]

7. Binding energies of 16, 8O and 35,17Cl are 127.35 MeV and 289.3 MeV respectively.Which of the two nuclei are more stable? [2]

8. THE total energy of an electron in the first excited state of hydrogen atom is -34.eV.

Calculate

(1) K.E. of the electron in this state.

(2) P.E. of the electron in this state and

(3) Which of the answer would change of the choice. Justify your answer?

9. Prove that the speed of election in the ground sate of hydrogen atom is equal to the speed of electron in the first excited state of hydrogen like Li++ atom. [3]

10. Draw a graph showing variation of potential energy of a pair of nucleon as a function of their separation indicate the region in which the nuclear force is (a) Attractive (b) Repulsive. Also write two characteristics features which distinguish it from the coulomb’s force. [3]

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