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A freshly prepared radioactive sample of...

A freshly prepared radioactive sample of half life 1 hour emits radiations that are 128 times as intense as the impossible safe limit. The minimum time after which this sample can be safely used is

A

`14hr`

B

`7hr`

C

`128hr`

D

`256hr`

Text Solution

Verified by Experts

The correct Answer is:
B
`T=1hr. (N)/(N_(0))=1/128 =(1/2)^(7)`
`:. n=7` As `t=nT`
`:. t=7xx1=7xx1=7hr`
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