1.

The radioactivity of a certain radioactive element drops to `1//64` of its initial value in `30` seconds. Its half-life is.A. 2 secondsB. 4 secondsC. 5 secondsD. 6 seconds

Answer» Correct Answer - C
( c) `N = N_0 ((1)/(2))^(t//T) rArr (N_0)/(64) = N_0 ((1)/(2))^(30//T)`
`rArr T = (30)/(6) = 5 sec`.


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