A radioactive substance has an average life of $5$ hours. In a time of $5$ hours
Half of the active nuclei decay
Less than half of the active nuclei decay
More than half of the active nuclei decay
All active nuclei decay
Consider two nuclei of the same radioactive nuclide. One of the nuclei was created in a supernova explosion $5$ billion years ago. The other was created in a nuclear reactor $5$ minutes ago. The probability of decay during the next time is
Two radioactive materials $X_1$ and $X_2$ have decay constant $5\lambda$ and $\lambda$ respectively intially they have the saame number of nuclei, then the ratio of the number of nuclei of $X_1$ to that $X_2$ will be $\frac{1}{e}$ after a time
A radioactive nucleus (initial mass number $A$ and atomic number $Z$ emits $3 \alpha$. - particles and $2$ positrons. The ratio of number of neutrons to that of protons in the final nucleus will be
The decay constant of a radioactive element is $0.01$ per second. Its half life period is .......$sec$
Consider an initially pure $M$ gm sample of$_ A{X}$, an isotope that has a half life of $T$ hour, what is it’s initial decay rate ($N_A$ = Avogrado No.)