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JEE Main 202226 JulyMorning Shift
Exam
JEE Main
Year
2022
Date
26 July
Shift
Morning Shift
Subject
Physics
Chapter
Nuclear Physics

JEE Main 2022 · 26 July · Morning Shift · Physics · Nuclear Physics

The disintegration rate of a certain radioactive sample at any...

The disintegration rate of a certain radioactive sample at any instant is 42504250 disintegrations per minute. 1010 minutes later, the rate becomes 22502250 disintegrations per minute. The approximate decay constant is

(Take log⁡e1.88=0.63\log_{e}1 . 88 = 0 . 63)

Options

  1. A0.02min⁡−10 . 02\min^{- 1}
  2. B2.7min⁡−12 . 7\min^{- 1}
  3. C0.063min⁡−10 . 063\min^{- 1}
  4. D6.3min⁡−16 . 3\min^{- 1}

Correct answer

C. 0.063min⁡−10 . 063\min^{- 1}

Step-by-step solution

At t=0t = 0 disintegration rate A0=4250dpm{A}_{0} = 4250dpm

At t=10mint = 10min disintegration rate At=2250dpm{A}_{t} = 2250dpm

The activity of a sample at any time is given by,

At=A0e−\lambdat{A}_{t} = {A}_{0}{e}^{- \lambdat}

⇒2250=4250e−λ(10)⇒ 2250 = 4250{e}^{- \lambda\left(10\right)}

⇒10λ=ln42502250=ln⁡1.88⇒ 10\lambda = ln\dfrac{4250}{2250} = \ln 1 . 88

⇒λ=0.063min⁡−1⇒ \lambda = 0 . 063\min^{- 1}

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