Question

What was thompson working with when he discovered the cathode rays

Answer 1

Thomas discovered cathode rays when he was working with electrons. He was performing experiments with electrons when one of them became electrically charged and a beam of light came from it, this creating a cathode ray.

Answer 2

In 1897 British physicist J.J. Thomson showed the rays were composed of a previously unknown negatively charged particle, which was later named the electron.