Question

Which of these is correct for cathode rays in a discharge tube?
A. Independent of nature of cathode
B. Independent of the nature of the gas
C. Is observed in the presence of electric and magnetic field
D. All of the above

Answer 1

Hint: Cathode rays are electromagnetic waves . They are a beam of positive particles. The value for charge and mass is the same, regardless of the gas.
The nature of the cathode ray remains constant in every tube. Use the properties to eliminate the possible answers.

Complete step by step answer:
Michael Faraday began studying for electrical discharge in vacuum tubes known as cathode ray discharge tubes.
Cathode rays are independent of the gas and the material that the tube is made up of. All the gases have the same value for $\dfrac{e}{m}$ ration, where: $e = $ charge on the gas and $m = $ mass of the gas
It is also observed in electrical and magnetic fields.
Cathode rays start from the cathode and move towards the anode since they are positive .
Televisions employ the use of cathode ray tubes for producing fluorescence of the back of the telly screen.

So, the correct answer is Option D.

Note: Electrical discharge carried out id vacuum tubes lead to the discovery of canal rays which carry positively charged particles. Their properties in the electrical and magnetic field is different from the electron and cathode rays.

The Cathode ray tube experiment uses fluorescent substances to emit light. They work on the principle of excitation and de excitation of electrons. When an electron is excited to a higher energy level, it falls back to ground state while emitting energy in the form of light.