(Nuclear fusion is often introduced with the deuterium–tritium example, but the underlying ideas are fully general.)
Answer the following points related to energy release in nuclear fusion:
(i) Define (a) mass defect of a nucleus and (b) binding energy of a nucleus.
(ii) Using the graph of binding energy per nucleon versus mass number (qualitative description is sufficient), explain why the fusion of two very light nuclei leads to the liberation of energy.
(iii) A fusion plasma containing two positively charged nuclei must be heated to very high temperatures before they can fuse. Explain, in words, the physical reason for this temperature requirement.
(iv) State any two natural or technological situations where nuclear fusion is known or attempted.