CUET · PHYSICS · PYQ PAPER 2023
A freshly prepared radioactive sample of half life 1 hour emits radiations that are 128 times as intense as the permissible safe limit. What is the minimum time after which the sample can be safely used?
- A 256 h
- B 128 h
- C 14 h
- D 7 h
Answer & Solution
Correct Answer
(D) 7 h
Step-by-step Solution
Detailed explanation
\( \frac{I}{I_0} = \left(\frac{1}{2}\right)^{t/T} \) \( \frac{1}{128} = \left(\frac{1}{2}\right)^{t/1} \) \( \left(\frac{1}{2}\right)^7 = \left(\frac{1}{2}\right)^t \) \( t = 7 \) h
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