Question

J.J. Thomson's cathode-ray tube experiment demonstrated that

• A. cathode rays are streams of negatively charged ions
• B. all the mass of an atom is essentially in the nucleus
• C. the $\frac em$ of electrons is much greater than the $\frac em$ of protons
• D. the $\frac em$ ratio of the cathode ray particles changes when a different gas is placed in the discharge tube

Answer 1

Answer: (C)

the $\frac em$ of electrons is much greater than the $\frac em$ of protons

Answer 2

In Thomson's experiment, he found that the electron-to-mass ($\frac em$) ratio for cathode ray particles was the same regardless of the material of the electrodes or the gas inside the tube. This finding suggested that cathode rays consisted of particles (electrons) that were much lighter than atoms, which led to the conclusion that electrons were constituents of atoms and had a very high $\frac em$ ratio compared to protons.
Therefore,
($\frac em$)electron >> ($\frac em$)proton
[∴ ($\frac em$)proton = $\frac {1}{1837}$ ($\frac em$)electron]

Option (A) is not correct because cathode rays are streams of electrons, not negatively charged ions.
Option (B) is not related to Thomson's experiment, as it concerns the atomic nucleus, which was not part of his investigation.
Option (D) is also not directly related to Thomson's experiment. The experiment mainly dealt with electrons and their properties, not with the effect of different gases in the discharge tube.

So, the correct option is (C): the $\frac em$ of electrons is much greater than the $\frac em$ of protons