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MODEL PAPER 9 — Physics STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 SciencePhysicsMODEL PAPER 93 Marks
Question
Draw a plot showing the variation of binding energy per nucleon with mass number A. Write two important conclusions which you can draw from this plot. Explain with the help of this plot, the release in energy in the processes of nuclear fusion and fission.
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Answer

Image

Binding energy per nucleon as a function of mass number A.
Two important conclusions from this graph are:
i. Nuclear forces non-central and short ranged force.
ii. Nuclear forces between proton-neutron and neutron-neutron are strong and attractive in nature.
Explanation of Nuclear Fission: When a heavy nucleus (A ≥ 235 say) breaks into two lighter nuclei (nuclear fission), the binding energy per nucleon increases i.e, nucleons get more tightly bound. This implies that energy would be released in nuclear fission. 
Explanation of Nuclear Fusion: When two very light nuclei (A  ≤ 10) join to form a heavy nucleus, the binding is energy per nucleon of fused heavier nucleus more than the binding energy per nucleon of lighter nuclei, so again energy would be released in nuclear fusion.

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