On what factor does the intensity (brightness) of spectral lines depend?

The discovery of the nucleus of an atom was due to the experiment carried out by

Match the following:

$A$. Chadwick	$1$. Cathode rays
$B$. Rutherford	$2$. $X$-ray spectra
$C$. Moseley	$3$. Discovery of neutrons
$D$. $J$. $J$. Thomson	$4$. Nuclear atom model

State whether the following statements are true or false:
$(i)$ Faraday's electrolysis experiments and cathode ray discharge tube experiments prove that protons are located in the nucleus of the atom,while electrons are located outside the nucleus.
$(ii)$ In the year $1887$,Goldstein discovered the proton.
$(iii)$ In the year $1932$,the neutron was discovered by Chadwick.
$(iv)$ The first atomic model was proposed by Thomson.

When beryllium is bombarded with $\alpha$-particles,extremely penetrating radiations which cannot be deflected by electrical or magnetic field are given out. These are

Which particle leaves no track in a Wilson cloud chamber?