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Percentage of a radioactive element deca...

Percentage of a radioactive element decayed after 20 s when half-life is 4 s

A

92.25

B

96.87

C

50

D

75

Text Solution

Verified by Experts

The correct Answer is:
B
`n = (20)/(4) = 5, (N_(t))/(N_(0)) = ((1)/(2))^(5) = (1)/(32), :.` decayed
`= (1 -(1)/(32)) xx 100 = (31)/(32) xx 100 = 96.87`
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