Physics - Modern Physics Question with Solution | TestHub

From the formula

$\text{N}={\text{N}}_0{\left(\frac{1}{2}\right)}^{\text{n}}$

$\frac{\text{N}}{16}={\text{N}}_0{\left(\frac{1}{2}\right)}^{\text{n}}$

${\text{N}}_0=$original number of atom

${\left(\frac{1}{2}\right)}^4={\left(\frac{1}{2}\right)}^{\text{n}}$

$\Rightarrow$$\text{n}=4$

4 half lives

$\therefore$$4{\text{T}}_{1/2}=40$

$4{\text{T}}_{1/2}=\frac{40}{4}=10\text{ days}$