What percentage of original radioactive atoms is left after five half lives..........$\%$
$0.3$
$1$
$31$
$3.125$
During mean life of a radioactive element, the fraction that disintegrates is
The decay constant of radium is $4.28 \times {10^{ - 4}}$ per year. Its half life will be ..........$years$
Radon $({R_n})$ decays into Polonium (${P_0}$) by emitting an $\alpha - $ particle with half-life of $4\, days$. A sample contains $6.4 \times {10^{10}}$ atoms of $R_n$. After $12\, days$, the number of atoms of ${R_n}$ left in the sample will be
The half lives of a radioactive substance are $T$ and $2T$. years for $\alpha - $ emission and $\beta - $ emission respectively. The total de cay constnnt for simultaneous decay of $\alpha$ and $\beta$ adioactive substance is ___
$'Rn$' decays into $'Po'$ by emitting $a -$ particle with half life of $4\, days$. A sample contains $6.4 \times 10^{10}$ atoms of $Rn$. After $12\, days$, the number of atoms of $'Rn'$ left in the sample will be