A radioactive material has an initial amount $16\, gm$. After $120$ days it reduces to $1 \,gm$, then the half-life of radioactive material is ..........$days$

The count rate of a Geiger- Muller counter for the radiation of a radioactive material of half life of $30\, minutes$ decreases to $5\,{s^{ - 1}}$ after $2\, hours.$ The initial count rate was..........${s^{ - 1}}$

A radioactive nuclei with decay constant $0.5/s$ is being produced at a constant rate of $100\, nuclei/s$. If at $t\, = 0$ there were no nuclei, the time when there are $50\, nuclei$ is

Activity of a radioactive substance can be represented by various unit. Select correct option

Half-lives of two radioactive elements $A$ and $B$ are $20$ minutes and $40$ minutes, respectively. Initially, the samples have equal number of nuclei. After $80$ minutes, the ratio of decayed number of $A$ and $B$ nuclei will be

Two species of radioactive atoms are mixed in equal number. The disintegration constant of the first species is $\lambda$ and of the second is $\lambda / 3$. After a long time the mixture will behave as a species with mean life of approximately