For a certain radioactive substance, it is observed that after 4 hours, only 6.25% of the original sample is left undecayed. If follows that-
A
Thehalf life of the sample is 1 hour
B
The mean life of the sample is 
hour
hour
C
The decay constant of the sample is ln 2 hour –1
D
After a further 4 hours, the amount of the substance left over would by only 0.39% of the original amount
Text Solution
Verified by ExpertsThe correct answer is:
CHECK THE SOLUTION.
(a, b, c, d)
We have 6.25% = 
The given time of 4 hours thus equals 4 half-lives so that the half life is 1 hour.
Since half life 
and mean life = 
after further 4 hours, the amount left over would be 
or 0.39% of original amount.
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