A sample of rock from moon contains equal number of atoms of uranium and lead `(t""_(1//2)for U=4.5xx10""^(9)`year). The age of the rock would be

Options

A. `4.5xx10""^(9)` year
B. `9xx10""^(9)` year
C. `13.5xx10""^(9)` year
D. `2.25xx10""^(9)` year

Answer

a

Explanation

`lamdat=2.303log((U""^(238)+pb""^(206))/(U""^(238)))`
`lamda=0.693/t""_(1//2),txx0.693/t""_(1//2)=2.303 log2,t=t""_(1//2)`
`N=N""_(0)/2""^(n),2""^(n)=N""_(0)/N=15.2/7.6=2,n=1`