A $0.50\text{g}$ sample of rock was found to have $2.5\times {10}^{-6}\text{mol}$ of ${}_{19}^{40}K(t_{1/2}=1.3\times {10}^9\text{years})$ and $7.5\times {10}^{-6}{\text{mol of}}_{20}^{40}Ca$. How old is the rock?

Q. A $0.50\text{g}$ sample of rock was found to have $2.5\times {10}^{-6}\text{mol}$ of ${}_{19}^{40}K(t_{1/2}=1.3\times {10}^9\text{years})$ and $7.5\times {10}^{-6}{\text{mol of}}_{20}^{40}Ca$. How old is the rock?

Q. A radio isotope X with a half life $1.4\times {10}^9$ years decays to Y, which is stable. A sample of the rock from a cave was found to contain X and Y in the ratio 1 : 7. The age of the rock is

Q.

Half lives of two isotopes X and Y of a material are known to be $2\times {10}^9$ years and $4\times {10}^9$ years respectively. If a planet forms with equal number of these isotopes , estimate the current age of the planet, given that currently the material has 20% of X and 80% of Y by number

Q.

At radioactive equilibrium, the ratio between the number of the atoms of two radioactive elements (X) and (Y) was found to be $3.2\times {10}^9$ : 1 respectively. If half-life of the element (X) is $1.6\times {10}^{10}$ years, then half-life of the element (Y) would be

Q. A radioactive isotope $X$, having a half life $1.4\times {10}^9$ years, decays to $Y$ which is stable. A rock sample from a cave was found to contain $X$ and $Y$ in the ratio $1:7$. The age of the rock is,