A freshly prepared radioactive sample of half- life $1$ hour emits radiations that are $128$ times as intense as the permissible safe limit. The minimum time after which this sample can be safely used is .........$hours$

The half-life of a radioactive substance is $40$ years. How long will it take to reduce to one fourth of its original amount and what is the value of decay constant

The half lives of a radioactive substance are $T$ and $2T$. years for $\alpha  - $ emission and $\beta - $ emission respectively. The total de cay constnnt for simultaneous decay of $\alpha$ and $\beta$ adioactive substance is ___

Half life period of a radioactive sample is $T$. Let $x$ fraction disintegrates in time $'t'$. How much fraction will decay in $'\frac{t}{2}'$ time

At a given instant, say $t = 0,$ two radioactive substances $A$ and $B$ have equal activates. The ratio $\frac{{{R_B}}}{{{R_A}}}$ of their activities. The ratio $\frac{{{R_B}}}{{{R_A}}}$ of their activates after time $t$ itself decays with time $t$ as $e^{-3t}.$ If the half-life of $A$ is $ln2,$ the half-life of $B$ is

The half life of polonium is $140\, days$. After how many days, $16 \,gm$ polonium will be reduced to $1 \,gm$ .........$days$(or $15\,g$ will decay)