Question

(a) Draw the plot of binding energy per nucleon (BE/A) as a function of mass number A. Write two important conclusions that can be drawn regarding the nature of nuclear force. 

(b) Use this graph to explain the release of energy in both the processes of nuclear fusion and fission. 

(c) Write the basic nuclear process of neutron undergoing β –decay. Why is the detection of neutrinos found very difficult?

Answer 1

(a) Graphical variation of (BE/A) for nucleons with mass number A .
The variation of binding energy per nucleon versus mass number is shown infigure.

Conclusions: 

(i) Nuclear forces non-central and short ranged force. 

(ii) Nuclear forces between proton-neutron and neutron-neutron are strong and attractive in nature. 

(b) 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. 

(c) During decay of a neutron, we have 

₀¹n → ₁¹p + _-1⁰b + v bar 

The detection of neutrinos is very difficult because it shows weak interactions with other particles