MHT CET · Physics · Nuclear Physics
The half-life of a radioactive substance is 30 minutes. The time taken between \(40 \%\) decay and \(85 \%\) decay of the same radioactive substance is
- A 15 minutes
- B 90 minutes
- C 60 minutes
- D 30 minutes
Answer & Solution
Correct Answer
(C) 60 minutes
Step-by-step Solution
Detailed explanation
When \(40 \%\) nuclei decay, \(60 \%\) nuclei remain undecayed Let this number be \(\mathrm{N}_0\) When \(85 \%\) nuclei decay, \(15 \%\) nuclei remain undecayed This number will be \(\mathrm{N}=\frac{\mathrm{N}_0}{4}\)
The number of nuclei will become one-fourth in two half-lives i.e., 60 minutes.
The number of nuclei will become one-fourth in two half-lives i.e., 60 minutes.
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