What is the ratio of the mass of an electron to the mass of a proton?

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

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.

The size of the nucleus is of the order of

The masses of an electron,a proton and a neutron respectively will be in the ratio

The mass of a proton is $... \ g$.