CBSE Class 12 Physics Atoms Nuclei Frequently Asked Questions

CBSE Class 12 Physics Atoms Nuclei Frequently Asked Questions. There are many more useful educational material which the students can download in pdf format and use them for studies. Study material like concept maps, important and sure shot question banks, quick to learn flash cards, flow charts, mind maps, teacher notes, important formulas, past examinations question bank, important concepts taught by teachers. Students can download these useful educational material free and use them to get better marks in examinations.  Also refer to other worksheets for the same chapter and other subjects too. Use them for better understanding of the subjects.

ATOMS & NUCLEI

1. Define disintegration constant and mean life of a radioactive substance. Give the unit of each.

2. What is impact parameter? What is the value of impact parameter for a head on collision? The sequence of the stepwise decays of radioactive nucleus is:

If the nucleon number and atomic number for D₂ are respectively 176 & 71, what are 2 the corresponding values for D and D₄ nuclei? Justify your answer. 

3. Draw a diagram to show the variation of binding energy per nucleon with mass number for different nuclei. Explain with the help of this plot the release of energy in the processes of nuclear fission and fusion?

4. The value of ground state energy of hydrogen atom is: -13.6 eV; (i) what does the negative sign signify? & (ii) How much energy is required to take an electron in this atom from the ground state to the first excited state?

5. Give one point of difference between ‘nuclear fission’ & ‘nuclear fusion’. Will neutron to proto ratio increase or decrease in a nucleus when: (i) an electron, (ii) a positron is emitted?

6. Sketch the graph showing the variation of potential energy of a pair of nucleons as a function of their separation. Write three characteristic properties of nuclear force which distinguish it from the electrostatic force.

7. State two characteristics of nuclear force. Why does the binding energy per nucleon decrease with increase in mass number for heavy nuclei like ²³⁵U?

8. Define activity of a substance. State its S.I unit. Derive an expression for activity of a substance.

9. State the basic postulates of Bohr’s atomic model & derive an expression for the energy of an electron in any orbit of hydrogen atom.

10. Derive an expression for the radius of stationary orbit. Prove that the various stationary orbits are not equally spaced.

11. Derive mathematical expressions for: (i) kinetic energy, & (ii) potential energy of an electron revolving in an orbit of radius ‘r’; how does the potential energy change with increase in principal quantum number (n) for the electron and why?

12. Define the decay constant for a radioactive sample. Which of the following radiations α, β, & g rays are: (i) similar to X-rays? (ii) easily absorbed by matter? & (iii) similar in nature to cathode rays?

13. Define the terms: half life period and decay constant of a radioactive sample. Derive the relation between these terms.

14. In Rutherford’s scattering experiment, mention two important conclusions which can be drawn by studying the scattering of α particles by an atom. Draw the schematic arrangement of Geiger and Marsden experiment showing the scattering of α particle by a thin foil of gold. How does one get the information regarding the size of the nucleus in this experiment?

15. Sketch the energy level diagram for hydrogen atom. Mark the transitions corresponding to Lyman and Balmer series.

16. Prove that the instantaneous rate of change of the activity of a radioactive substance is inversely proportional to the square of its half life.

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