1.

A freshly prepared radioactive source of half-life `2 h` emits radiation of intensity which is 64 times the permissible safe level. The minimum time after which it would be possible to work safely with this source isA. `12 h`B. `24 h`C. `6 h`D. `130 h`

Answer» Correct Answer - a
For working safely, the activity must reduce to `(1)/(64)`
`(N)/(N_(0))=((1)/(2))^(n)=(1)/(64)`
`n=6`
`t= nt=6 xx 2= 12H`


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