In the uranium radioactive series,the initial nucleus is $_{92}U^{238}$ and the final nucleus is $_{82}Pb^{206}$. When the uranium nucleus decays to lead,the number of $\alpha$-particles emitted will be

$A$ radioactive nucleus of mass $M$ emits a photon of frequency $v$ and the nucleus recoils. The recoil energy will be

The nucleus ${ }_{Z}^{A} X$ undergoes the series of reactions given below:
${ }_{Z}^{A} X \stackrel{\alpha \text {-decay }}{\longrightarrow} P \stackrel{\beta \text {-decay }}{\longrightarrow} Q \stackrel{\alpha \text {-decay }}{\longrightarrow} R$
The number of neutrons in the nucleus $R$ 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)

$\beta$-decay means emission of electron from

In medicine,to destroy cancer cells . . . . . . rays are used.