A sample of rock moon contains equal numbers of atoms of uranium and lead `t_(1//2)` for `U` is `4.5 xx 10^(9)` years. The age of rock would be
a. `4.5 xx 10^(9)` years b. `9.0 xx 10^(9)` years
c. `13.5 xx 10^(9)` years d. `2.25 xx 10^(9)` years

Options

A. `9 xx 10^(9)` years
B. `4.5 xx 10^(9)` years
C. `13.5 xx 10^(9)` years
D. `2.25 xx 10^(9)` years

Answer

b

Explanation

`t = (2.303)/(lambda) log_(10) [1+("No. of Pb atoms")/("No. of atoms")]`
`= (2.303 xx 4.5 xx 10^(9)9)/(0.693) log_(10) (1 + 1)`