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Half life of radioactive element is 5 mi...

Half life of radioactive element is 5 min. At the end of 20 min its ________% quantity is disintegrated

A

6.25

B

75

C

25

D

93.75

Text Solution

Verified by Experts

The correct Answer is:
D
Half life `t_(1//2)` = 5 min
Total time t = 20 min
Number of half lives `=20/5=4`
`rArrN/(N_0)=[1/2]^(h)=[1/2]^4`
`rArrN/(N_0)=1/16`
`N=(N_0)/16`
Disintegrated `yrArr[(N_0-N)/(N_0)]x100=[1-N/(N_0)]x100`
`rArr[1-1/16]xx100=93.75%`
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