COMEDK · Physics · 29. Nuclear Physics
A count rate meter shows a count of 240 per min from a given radioactive source. One hour later the meter shows a count rate of 30 per min. The half-life of the source is
- A \(20 \mathrm{~min}\)
- B \(30 \mathrm{~min}\)
- C \(80 \mathrm{~min}\)
- D \(120 \mathrm{~min}\)
Answer & Solution
Correct Answer
(A) \(20 \mathrm{~min}\)
Step-by-step Solution
Detailed explanation
Let \(N\) be the amount of substance left, \(N_{0}\) be the total amount of substance. The amount of substance left after \(N\) half-life is given by \(\quad \frac{N}{N_{0}}=\frac{1}{2^{n}}\) Hence, \(\quad \frac{30}{240}=\frac{1}{2^{n}}\) (Since, decay rate proportional to…
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