The half-life period of radium is $1600 $ years. Its average life time will be.......years
$3200$
$4800$
$2319$
$4217$
At a given instant there are $25\%$ undecayed radioactive nuclei in a same. After $10 \,sec$ the number of undecayed nuclei reduces to $6.25\%$, the mean life of the nuclei is...........$ sec$
A radioactive substance has a half-life of $1$ year. The fraction of this material, that would remain after $5$ years will be
Who invented radioactivity ?
The graph between number of decayed atoms $N'$ of a radioactive element and time $t$ is
The decay constant of a radioactive element is $1.5 \times {10^{ - 9}}$ per second. Its mean life in seconds will be