Radioactivity is

$A$ radioactive nucleus of mass number $A$,initially at rest,emits an $\alpha$-particle with a speed $v$. The recoil speed of the daughter nucleus will be

$A$ 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 $..................$

$A$ nucleus $_n{X^m}$ emits one $\alpha$ particle and two $\beta$ particles. The resulting nucleus is

In an $\alpha$-decay,the kinetic energy of the $\alpha$-particle is $48 \, MeV$ and the $Q$-value of the reaction is $50 \, MeV$. The mass number of the mother nucleus is: (Assume that the daughter nucleus is in the ground state)

Beta rays emitted by a radioactive material are