At a specific instant,the emission of a radioactive compound is deflected in a magnetic field. The compound can emit:
$(i)$ Electrons
$(ii)$ Protons
$(iii)$ $He^{2+}$
$(iv)$ Neutrons
The emission at that instant can be:

The energy spectrum of $\beta$-particles [number $N(E)$ as a function of $\beta$-energy $E$] emitted from a radioactive source is:

Which of the following can penetrate through an aluminum sheet of $20 \, cm$ thickness?

In the following nuclear reaction,$D \xrightarrow{\alpha} D_{1} \xrightarrow{\beta^-} D_{2} \xrightarrow{\alpha} D_{3} \xrightarrow{\gamma} D_{4}$. The mass number of $D$ is $182$ and the atomic number is $74$. The mass number and atomic number of $D_{4}$ respectively will be:

$\beta$-decay means emission of electron from

Radioactivity is