Which of the following statements regarding cathode rays is incorrect?

Proton was discovered by

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.

Which of the following pairs has the identical $e/m$ value?

Alpha particles are $...$ times heavier (approximately) than neutrons.

The radius of the nucleus is related to the mass number $A$ by