Question

What are cathode rays made of according to J. J. Thomson?

Answer 1

Hint: The British physicist, J. J. Thomson performed a cathode ray tube experiment to know the properties of a beam of particles that comes from the cathode in it and showed that cathode rays were composed of a previously unknown negatively charged particle that was later named as the electron.

Complete answer:
Let us discuss about the cathode ray tube and cathode rays that comes out of it:-
-In the late ${{19}^{th}}$century, physicist J.J. Thomson began his experiment with cathode ray tubes. These are the sealed glass tubes from which most of the air has been evacuated. When a high voltage is applied across two electrodes at one end of the tube, it causes a beam of particles to flow from the cathode (the negative charged electrode) to the anode (the positive charged electrode).
-These tubes are called cathode ray tubes as the particle beam or "cathode ray" emerges from the cathode. This cathode ray can be detected by painting a material such as phosphors onto the far end of the tube beyond the anode. When the cathode ray comes out, the phosphors spark or emit light.
-To test the properties of the particles, J. J. Thomson placed two oppositely charged electric plates around the cathode ray. He observed that the cathode ray was deflected away from the negatively charged electric plate and towards the positively charged plate which indicated that the cathode ray was composed of negatively charged particles.
-Thomson made the conclusion that the cathode ray is composed of negatively charged particles which were later named as electrons.

Note:
To verify his observation, he repeated his experiments using different metals as electrode materials and ultimately found that the properties of the cathode ray remained constant no matter what cathode material they originated from hence proving his theory to be correct.