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A freshly prepared radioactive source of...

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 is

A

`6h`

B

`12 h`

C

`24 h`

D

`128 h`

Text Solution

Verified by Experts

The correct Answer is:
b
`(A)/(A_(0)) =(N)/(N_(0))`
Let safe level avtivity be `A`. Initial activity =`64 A`.
Hence, `(N)/(N_(0)) =(A)/(A_(0))=(A)/(64A)=(1)/(64)`
or `((1)/(2))^(n)=(1)/(64)` or `n=6`
Hence, `(t)/(T) =n=6`
`becauseT=2h`
`:. t= 12 h`.
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