List of top Physics Questions on Half life asked in AP EAPCET

The half-life of a radioactive substance is 20 minutes. $\frac{1}{3}$rd part of substance has decayed in time $t_1$ and $\frac{2}{3}$rd part of it has decayed in time $t_2$. Then, ($t_2 - t_1$) is nearly

If decay constant of a radioactive element doubles, then its half-life time becomes: