The mean life time of a radionuclide, if its activity decrease by $4\%$ for every $1h$ , would be  .......... $h$ [product is non-radioactive i.e. stable]

A sample contains $16\, gm$ of a radioactive material, the half life of which is two days. After $32\, days,$ the amount of radioactive material left in the sample is

The decay constant of a radio isotope is $\lambda$. If  $A_1$ and $A_2$ are its activities at times $t_1$ and $t_2$  respectively, the number of nuclei which have decayed during the time $(t_1 - t_2)$ 

The rate of disintegration was observed to be ${10^{17}}$ disintegrations per sec when its half life period is $1445$ years. The original number of particles are

Activity of a radioactive sample decreases to $(1/3)^{rd}$ of its original value in $3\, days$. Then, in $9\, days$ its activity will become

The half life of radium is $1620$ years and its atomic weight is $226\, k\,gm$ per kilomol. The number of atoms that will decay from its $1\, gm$ sample per second will be

(Avogadro's number $N = 6.02 \times {10^{26}}$atom/kilomol)