Radon `(Ra)` decays into Polonium `(P_0)` by emitting an `alpha-`particle with half-life of `4` days. A sample contains `6.4 xx 10^10` atoms of `R_n`. After `12` days, the number of atoms of `R_n` left in the sample will be

Options

A. `3.2 xx 10^10`
B. `0.53 xx 10^10`
C. `2.1 xx 10^10`
D. `0.8 xx 10^10`

Answer

D

Explanation

(d) In the given case, `12` days = `3` half-lives Number of atoms left after `3` half-lives,
=`6.4 xx 10^10 xx (1)/(2^3) = 0.8 xx 10^10`.