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 \(80 \mathrm{~min}\)
- B \(120 \mathrm{~min}\)
- C \(20 \mathrm{~min}\)
- D \(30 \mathrm{~min}\)
Answer & Solution
Correct Answer
(C) \(20 \mathrm{~min}\)
Step-by-step Solution
Detailed explanation
In radioactive decay, the decay rate is proportional to the amount of substance. So, for change of count rate from 240 per min to 30 per min, let \(N\) be the number of half-life passed in one hour. Then, \(\frac{240}{2^{N}}=30\) \(\Rightarrow \quad 2^{N}=8\)…
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