At any instant the ratio of the amount of radioactive substances is $2 : 1$. If their half lives be respectively $12$ and $16$ hours, then after two days, what will be the ratio of the substances
$ 1 : 1$
$2 : 1$
$1 : 2$
$1 : 4$
A radioactive element ${ }_{92}^{242} X$ emits two $\alpha$-particles, one electron and two positrons. The product nucleus is represented by ${ }_{ P }^{234} Y$. The value of $P$ is $..................$
The half-life of $Au ^{198}$ is $2.7\, days.$ The activity of $1.50\, mg$ of $Au ^{198}$ if its atomic weight is $198\, g mol ^{-1}$ is .......$Ci$ $\left( N _{ A }=6 \times 10^{23}\, / mol \right)$
Write the definition of half life of radioactive substance and obtain its relation to decay constant.
Which of the following is not a mode of radioactive decay
Out of the following, which one is not emitted by a natural radioactive substance?