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A radioactive sample has 8.0 xx 10^18 ac...

A radioactive sample has `8.0 xx 10^18` active nuclei at a certain instant. How many of these nuclei will still be in the same active state after two half-lives?

Text Solution

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In one half-life the number of active nuclei reduces to half the original number. Thus, in two half-lives the number is reduced to `(1/2) (1/2)` of the original number. The number of remaining active nuclei is, therefore,
`6.0 xx 10^18 xx(1/2) xx (1/2)`
`= 1.5 xx 10^18`
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