Question

The ratio of $e/m$, i.e., specific charge for a cathode ray:

• A. has the smallest value when the discharge tube is filled with $H_2$.
• B. is constant.
• C. varies with the atomic number of gas in the discharge tube.
• D. varies with the atomic number of an element forming the cathode.

Answer 1

Answer: (B)

is constant.

The ratio of e/m,(charge/mass) i.e., specific charge for a cathode ray is constant.
cathode rays are made of electrons and independent of medium used.
Mass of electron $=m_e$ and
Charge of electron $=e$ So $e/m=e/m_e=1.75882008839\times {10}^{11}$ C/kg $=$ constant