Question 621: Atoms & Nuclei

Question

Polonium has a half-life of 140 days. If we take $20 \mathrm{~g}$ of polonium initially then the amount of it that remains after 280 days is

Accepted Answer

After $n$-half lines quantity of radiatioactive substance left is
$N=N_0\left(\frac{1}{2}ight)^{t / T_{1 / 2}}$
$\begin{aligned}
	ext { Given, } T_{1 / 2} & =140 	ext { days, } t=28 	ext { days, } \
N_0 & =20 \mathrm{~g} \
	herefore \quad \quad N & =20\left(\frac{1}{2}ight)^{\frac{280}{140}}=\frac{20}{4}=5 \mathrm{~g}
\end{aligned}$

Answer

2.5 g

Answer

5 g

Answer

10 g

Answer

15 g

Atoms & Nuclei

Polonium has a half-life of 140 days. If we take 20 \mathrm{~g} of polonium initially then the amount of it that remains after 280 days is

Choose the correct answer: