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The Decay Constant of a Radioactive Sample is λ. the Half-life and the Average-life of the Sample Are Respectively - Physics


The decay constant of a radioactive sample is λ. The half-life and the average-life of the sample are respectively


  • 1/λ and (In 2/λ)

  • (In 2/λ) and 1/λ

  • λ(In 2) and 1/λ

  • λ/(In 2) and 1/λ.

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(ln 2/λ) and 1/λ

The half-life of a radioactive sample `(t_(1"/"2))`  is defined as the time elapsed before half the active nuclei decays.

Let the initial number of the active nuclei present in the sample be `N_0` .

`N_0/2 = N_0e^(-lambdat_"1/2")`

⇒ `t_"1/2" = ("In 2")/lambda`

Average life of the nuclei, `t_(av) = S/N_0 = 1/lambda`

Here, S is the sum of all the lives of all the N nuclei that were active at t = 0 and  `lambda` is the decay constant of the sample.

Concept: Radioactivity - Law of Radioactive Decay
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HC Verma Class 11, Class 12 Concepts of Physics Vol. 2
Chapter 24 The Nucleus
MCQ | Q 15 | Page 441
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