Nuclear Physics And Radioactivity Question 293
Question: The count rate of a Geiger- Muller counter for the radiation of a radioactive material of half life of 30 minutes decreases to 5 $ {{s}^{-1}} $ after 2 hours. The initial count rate was [CBSE PMT 1995]
Options:
A) 25 $ {{s}^{-1}} $
B) 80 $ {{s}^{-1}} $
C) 625 $ {{s}^{-1}} $
D) 20 $ {{s}^{-1}} $
Show Answer
Answer:
Correct Answer: B
Solution:
$ A=A_{0}{{( \frac{1}{2} )}^{t/{T_{1/2}}}} $
Þ $ 5=A_{0}{{( \frac{1}{2} )}^{\frac{2\times 60}{30}}}=\frac{A_{0}}{16} $
Þ $ A_{0}=80,se{{c}^{-1}} $
BETA
