Alpha rays emitted from a radioactive substance are

The plot of the number $(N)$ of decayed atoms versus activity $(A)$ of a radioactive substance is

The half life of a radioactive nucleus is $50$ days. The time interval $\left( t _2-t_1\right)$ between the time $t _2$ when $\frac{2}{3}$ ot it has decayed and the time $t_1$, when $\frac{1}{3}$ of it had decayed is ......days

The decay constant of a radioactive element is $0.01$ per second. Its half life period is .......$sec$

Half life of a radioactive element is $10\, days$. The time during which quantity remains $1/10$ of initial mass will be .........$days$

In a radioactive material the activity at time $t_1$ is $R_1$ and at a later time $t_2$ it is $R_2$. If the decay constant of the material is $\lambda$ then