The beta activity of `1 g` of carbon made from green wood is 15.3 counts per minute. If the activity of `1 g` of carbon derived from the wood of an Egyptian mummy case is 9.4 counts per minute under the same conditions, how old is the wood of the mummy case?

Explanation

` K = 0.693//t_(1//2) = 0/693//5770`
`= 1.20 xx 10^(4) "year"^(-1)`
log `N_(0)//N_(1) = Kt//2.303`
`1.20 xx 10^(-4) xx t//2.303 = "log" N_(0)//N_(t)`
`"log" 15.3//9.4`
Hence `t = 2.303//1/20 xx 10^(-4) "log" 15.3//9/4`
`= 3920` years