Questions
At given instant there are 50% undecayed radioactive nuclei in a sample. After 20sec, the number of undecayed nuclei reduces to 12.5% . Calculate mean life of the nuclei.
a
20 s
b
14.43 s
c
10 s
d
15 s
detailed solution
Correct option is B
The no of undecayed nuclei is reduced from 50% to 25% to 12.5% (i.e, two half ) in 20 sec. ∴The half life of the radioactive sample = T12=202 =10 s Now, Half life= T12=0.693λ ⇒ λ=0.693t12 Mean life = Ta=1λ=T120.693=100.693=14.43secTalk to our academic expert!
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