The e/m ratio of cathode does not depend on the nature of the gas filled in the discharge tube. Give reasons.
Cathode rays are beam of electrons which are negatively charged. These electrons are identical. Hence, the charge to mass ratio (e/m) of cathode rays is same for all the gases.
Whereas, in case of anode rays, they are positively charged. Also, they are composed of ionised nuclei which vary from gas to gas in terms of atomic number and mass number. Thus, charge to mass ratio (e/m) of the positively charged ions changes as the number of nucleons changes in the nucleus of each gas can be different.