Question

There are ${10}^6$ radioactive nuclei in a given radioactive element. Its half life is $20$ seconds. How many nuclei will remain after $10$ seconds? (Given, $\sqrt{2}=1.41$)

Answer 1

$N=N_0{\left(\frac{1}{2}\right)}^n={10}^6\times {\left(\frac{1}{2}\right)}^{1/2}$ as $n=\frac{10}{20}=\frac{1}{2}$

$=\frac{{10}^6}{1.41}=7.09\times {10}^5$