The half life of a radioactive substance is 20 minutes. The time taken between 
decay and 
decay of the substance will be
Text Solution
Verified by ExpertsThe correct answer is:
A
Let in time 
of the substance decay and in time 
of the substance decay. Then in time 
of the substance left undecayed and in time 
of the substance left undecayed.
According to radioactive decay law
where 
is the decay constant.
or 
or 
. (i)
and 
or 
(ii)
Dividing eqn. (ii) by eqn. (i), we get
or 
Here, 
minutes
minutes 
minutes
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