Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main 202125 JulyMorning Shift
Exam
JEE Main
Year
2021
Date
25 July
Shift
Morning Shift
Subject
Physics
Chapter
Nuclear Physics

JEE Main 2021 · 25 July · Morning Shift · Physics · Nuclear Physics

Some nuclei of a radioactive material are undergoing radioactive...

Some nuclei of a radioactive material are undergoing radioactive decay. The time gap between the instances when a quarter of the nuclei have decayed and when half of the nuclei have decayed is given as: (where λ\lambda is the decay constant)

Options

  1. A12ln⁡2λ\dfrac{1}{2}\dfrac{\ln 2}{\lambda}
  2. Bln⁡2λ\dfrac{\ln 2}{\lambda}
  3. C2ln⁡2λ\dfrac{2\ln 2}{\lambda}
  4. Dln32λ\dfrac{ln\dfrac{3}{2}}{\lambda}

Correct answer

D. ln32λ\dfrac{ln\dfrac{3}{2}}{\lambda}

Step-by-step solution

3N04=N0e−λt1\dfrac{3{N}_{0}}{4} = {N}_{0}{e}^{- \lambda{t}_{1}}

N02=N0e−λ2\dfrac{{N}_{0}}{2} = {N}_{0}{e}^{- {\lambda}_{2}}

ln⁡(3/4)=−λt1…(1)\ln \left(3 / 4\right) = - \lambda{t}_{1} \ldots ( 1 )

ln⁡(1/2)=−λt2…(2)\ln \left(1 / 2\right) = - \lambda{t}_{2} \ldots ( 2 )

ln⁡(3/4)−ln⁡(1/2)=λ(t2−t1)…(3)\ln \left(3 / 4\right) - \ln \left(1 / 2\right) = \lambda\left({t}_{2} - {t}_{1}\right) \ldots ( 3 )

\Deltat=ln⁡(3/2)λ\Deltat = \dfrac{\ln \left(3 / 2\right)}{\lambda}

Practice Nuclear Physics on Quantrex Academy →

More from Nuclear Physics

A nuclear reactor starts producing a radioactive nuclide X from t = 0 , at a constant… JEE Advanced 2026Two radioactive substances A and B of mass numbers 200 and 212 respectively, shows… JEE Main 2026The energy released if hydrogen atoms are combined to form ^ 4 _ 2 He is __________ MeV.… JEE Main 2026The energy released when (7)/(17.13) kg of ^ 7 _ 3 Li is converted into ^ 4 _ 2 He by… JEE Main 2026Assuming the experimental mass of ^ 12 _ 6 C as 12 u , the mass defect of ^ 12 _ 6 C atom… JEE Main 2026Two nuclei of mass number 3 combine with another nucleus of mass number 4 to yield a… JEE Main 2026The binding energy per nucleon of ^ 209 _ 83 Bi is _______ MeV. [Take m(^ 209 _ 83 Bi) =… JEE Main 2026A nucleus has mass number α and radius R_ α . Another nucleus has mass number β and… JEE Main 2026 Full Nuclear Physics list All JEE Main PYQs