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⚛️ Physics  ·  Nuclei  ·  NEET & JEE

Radioactive decay constant lambda is related to half-life by:

Answer: lambda = ln2 / T(1/2).

  • A lambda = ln2 x T(1/2)
  • B lambda = ln2 / T(1/2)
  • C lambda = T(1/2)/ln2
  • D lambda = 1/T(1/2)

Correct answer: B. lambda = ln2 / T(1/2)

Explanation: lambda = 0.693/T(1/2). Activity A = lambda x N = A<sub>0</sub> x e<sup>-lambda t</sup>.

Binding Energy per Nucleon vs Mass NumberMass number ABE/nucleonFe-56 (peak, most stable)FUSION region (light → medium)FISSION region (heavy → medium)Both processes release energy by moving nuclei toward the Fe-56 peak

Binding energy per nucleon rises sharply for light nuclei, peaks around iron-56 (the most stable nucleus), then slowly declines for heavier nuclei - which is exactly why fusing light nuclei or splitting heavy nuclei both release energy: each moves the products toward this stability peak.

Concept context

Radioactivity, nuclear reactions, fission, fusion, and binding energy.

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