The increasing order for the values of $e/m$ $(\text{charge/mass})$ is :

The volume of an atom is $10^5$ times the volume of its nucleus. If we consider the ratio of the radius of an atom to the radius of its nucleus,it is approximately $10^5$. Since volume $V = \frac{4}{3} \pi r^3$,the ratio of volumes is $(\frac{r_{atom}}{r_{nucleus}})^3 = (10^5)^3 = 10^{15}$. Therefore,the volume of an atom is $10^{15}$ times the volume of the nucleus. Choose the correct factor.

Fill in the blanks given below:
$(i)$ The circular path around the nucleus in which electrons revolve at high speed is called ......... .
$(ii)$ Electrons and the nucleus are held together by ......... force.
$(iii)$ The number of $P^{+}$ in the nucleus and the sum of the number of $P^{+}$ and $n^{\circ}$ in the nucleus are represented by the symbols ...... and ......... respectively.
$(iv)$ The sum of the number of $P^{+}$ and $n^{\circ}$ in the nucleus is represented by the term ...... and the symbol .... respectively.

The positron was discovered by

Among the following,the correct statement about the cathode ray discharge tube is:

Rutherford's alpha-particle scattering experiment first showed that the atom has a .......