NCERT Physics Class 12 Exemplar Ch 13 Nuclei Part 1 (For CBSE, ICSE, IAS, NET, NRA 2023)

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Very Short Answer

11 And nuclei have the same mass number. Do they have the same binding energy?


  • No, the binding energy of is greater.

12 Draw a graph showing the variation of decay rate with number of active nuclei.


Draw a Graph Variation of Decay Rate Umber of Active Nuclei

13 Which sample, A or B shown in Fig. has shorter mean-life?

A or B Shown in Fig Has Shorter Mean-Life


  • B has shorter mean life as is greater for B.

14 Which one of the following cannot emit radiation and why?

Excited nucleus, excited electron.


  • Excited electron because energy of electronic energy levels is in the range of , only not in MeV.
  • As -radiation has energy in MeV.

15 In pair annihilation, an electron and a positron destroy each other to produce gamma radiation. How is the momentum conserved?


  • photons are produced which move in opposite directions to conserve momentum.