Question

Assertion:
The characteristics of cathode rays do not depend upon the material of electrodes and the nature of the gas present in the cathode ray tube
Reason:
Cathode rays consist of negatively charged particles, called electrons.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
C. Assertion is correct but Reason is incorrect.
D. Both Assertion and Reason are incorrect.

Answer 1

Hint: William crooks carried out discharge tube experiments and discovered a new type of rays and called them cathode rays in 1878. After that, J.J Thomson studied the characteristics of the cathode rays and found that they were made of negatively charged particles which were later named as electrons. The name electron was given by Johnson Stoney.

Complete Solution :
There are some characteristics of cathode rays which were given after studying them such as:
1) They start from the cathode and move towards the anode.
2) These rays are not visible to naked eyes but can be viewed under a phosphorescent material such as Zinc Sulphide, e.g. Tube light.
3) Their behaviour is similar to that of negatively charged particles in presence of electric and magnetic fields.
4) In absence of electric and magnetic fields, these rays travel in the same line.
5) The characteristics of cathode rays don’t depend on the material of electrodes and the nature of the gas present in them.
Hence, it is true that characteristics of cathode rays do not depend upon the material of electrodes and the nature of gas present in the cathode ray tube. It is also true that cathode rays consist of negatively charged particles, called electrons. But the reason is not the explanation of the assertion.
So, the correct answer is “Option B”.

Note: The reason behind the assertion is that the rays which are emitted from the cathode in the cathode tube are called cathode rays and the rays which are emitted in the discharged tube are electrons which are produced due to the ionisation of the cathode.