Physics Question on Semiconductor electronics: materials, devices and simple circuits

Question

The half-life of the radioactive radon is 3.8 days. The time, at the end of which 1/20th of the radon sample will remain undecayed, is (given $log_{10} e = 0.4343$ )

Answer 1

Solution

The correct option is(B): 16.5 days.

Using $N=N_0e^{-\lambda t}$
Where $\lambda=\frac{1n2}{t_{1/2}}=\frac{1n(2)}{3.8}$
$\therefore$ $\frac{N_0}{20}=N_0e^{-\frac{1n(2)}{3.8}}t$
Solving this equation with the help of given data we find :
t = 16.5 days.