Q. The nuclide $\ ^{131}I$ is radioactive, with a half-life of $8.04\ days$. At noon on January 1, the activity of a certain sample is $600\ Bq$. The activity at noon on January 24 will be
A) $75\ Bq$
B) Less than $75\ Bq$
C) More than $75\ Bq$
D) $150\ Bq$
Explanation
(c) Number of days from January 1$^{st}$ to January 24$^{th}$ = 23 days
Number of half lives $n = \frac{23}{8.04} = 2.86( < 3)$
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In three half lives activity becomes $75\ Bq$, but the given number of half lives are lesser than 3 so activity becomes greater than $75\ Bq$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.