Nuclear Physics And Radioactivity Question 101
Question: A radioactive substance has a half-life of 60 minutes. After 3 hours, the fraction of atom that have decayed would be
Options:
A) 12.5%
B) 87.5%
C) 8.5%
D) 25.1%
Show Answer
Answer:
Correct Answer: B
Solution:
[b] $ N=N_{0}{{( \frac{1}{2} )}^{\frac{t}{{T_{1/2}}}}} $ Hence, fraction of atoms decayed $ =1-\frac{N}{N_{0}}=1-{{( \frac{1}{2} )}^{\frac{t}{{T_{1/2}}}}}=1-{{( \frac{1}{2} )}^{\frac{3\times 60}{60}}}=\frac{7}{8} $ In percentage it is $ \frac{7}{8}\times 100=87.5% $
BETA
