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

The mass of an electron is ......... compared to the mass of the lightest nucleus.

The radius of an atom is about

$A$ particle having the same charge and $200$ times greater mass than that of an electron is:

The nucleus of an atom can be assumed to be spherical. The radius of the nucleus of mass number $A$ is given by $1.25 \times 10^{-13} \times A^{1/3} \ cm$. The radius of the atom is $1 \ \mathring{A}$. If the mass number is $64$,then the fraction of the atomic volume that is occupied by the nucleus is:

Identify the correct increasing order of $e/m$ ratio for the following particles: $n, p, e, \alpha$.