Nuclear Physics And Radioactivity Question 61
Question: From a newly formed radioactive substance (Half life 2 hours), the intensity of radiation is 64 times the permissible safe level. The minimum time after which work can be done safely from this source is [IIT 1983; SCRA 1996; DCE 2000; DPMT 2005]
Options:
A) 6 hours
B) 12 hours
C) 24 hours
D) 128 hours
Show Answer
Answer:
Correct Answer: B
Solution:
$ \frac{N}{N_{0}}={{( \frac{1}{2} )}^{n}}\Rightarrow \frac{1}{64}={{( \frac{1}{2} )}^{6}}={{( \frac{1}{2} )}^{n}}\Rightarrow n=6. $ After 6 half lives intensity emitted will be safe. \ Total time taken $ =6\times 2=12,hrs. $
BETA
