Question

Which of the following statements is not correct about the characteristics of cathode rays?
A. They start from the cathode and move towards the anode.
B. They travel in a straight line in the absence of an external electrical or magnetic field.
C. Characteristics of cathode rays do not depend upon the material of electrodes in a cathode ray tube.
D. Characteristics of cathode rays depend upon the nature of gas present in the cathode ray tube.

Answer 1

Hint: Cathode rays consist of negatively charged particles commonly called electrons whereas anode rays consist of positively charged particles known as protons. Thomson discovered cathode rays and they can move from cathode to anode i.e. from negative to positive end.

Complete answer:
The characteristics of cathode rays are:
> As cathode rays are negatively charged particles they travel from cathode to the anode end which is positively charged.
So, option A is the correct statement.
> Just like a wave, cathode rays also travel in the straight line in the absence of an electrical and magnetic field because when an object is placed in the path of a cathode ray they strike on it and produce a shadow.
So, option B is also the correct statement.
> As it is observed that cathode rays are deflected by the electrical and magnetic field similarly as the negative particles deflect because cathode rays are made of negatively charged particles.
> Cathode does not depend on both the material of electrode and nature of the gas that is filled in the discharged tube because the ratio of e/m. Here e is the charge and m is the mass of the electron.
So, option C is the correct statement but option D is an incorrect statement.

Therefore, option D is the correct answer.

Note: e/m is the ratio of the charge to mass of the particle. The value of e/m ratio is different in the case of anode rays. And that’s why it depends on the material of the electrode and nature of the gas present in the discharged tube.