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 e/m of electrons is much greater than the e/m of protons
• D. the e/m ratio of the cathode-ray particles changes when a different gas is placed in the discharge tube

Answer 1

Answer: (C)

$JJ$ Thomson's cathode-ray tube experiment demonstrated the relation for $e/m$ of charged particles. The relation is
$\frac{e}{m}=\frac{E^2}{2B^{2}V}$
Thus, knowing $E,B$ and $V$, the value of $e/m$ for electrons and for protons can be calculated. It is found the $e/m$ of electrons is much greater than the $e/m$ of protons.