1.

The activity of a radioactive substance reduces to (1)/(32) of its initial value in 22.5 xx 10^9 yrs. Find its disintegration constant :

Answer»

`1.54 xx 10^(-10)//yr`
`4.5 xx 10^(-9)//yr`
`5.25 xx 10^(-8)//yr`
`7.25 xx 10^(-7)//yr`

Solution :If n is no. of half LIVES, then
`A/A_(0)=[1/2]^(n) rArr 1/(32)=(1/2)^(n) rArr (1/2)^(5)=(1/2)^(n)`
n=5
ALSO, `n=t/T rArr T=t/n`
i.e. `T=(22.5 xx 10^(9))/(5)=4.5 xx 10^(9) yrs`


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