Positive rays were used in the discovery of the proton. These rays were produced from
- A. the cathode of the discharge tube
- B. the residual gas atoms losing electrons in a discharge tube
- C. the radioactive decay of uranium
- D. the anode metal evaporating
Explanation
Goldstein observed that cathode rays travelling through a perforated cathode knocked electrons off the residual gas atoms, leaving positive ions that streamed towards the cathode as canal rays. Their charge to mass ratio depended on which gas was in the tube, and it was largest for hydrogen, identifying the proton. Cathode rays themselves are electrons and come from the cathode.