What percentage of radioactive substance is left after five half - lives? - Physics

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What percentage of radioactive substance is left after five half-lives?

Options

  • 20 %

  • About 97 %

  • About 3 %

  • 5 %

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Solution

About 3 %

Explanation:

`"N"_0/"N" = 2^5`

`therefore "N"/"N"_0 = 1/2^5`

`therefore "N"/"N"_0 xx 100 = 100/32 =  3.125`%

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