Which subatomic particle was discovered by researchers working with cathode-ray tubes?

• A. Positron
• B. Neutron
• C. Proton
• D. Electron

Answer: (D)

Verified step by step guidance

1. Understand the context of the question: it asks which subatomic particle was discovered using cathode-ray tubes, a key experimental tool in early atomic physics.
2. Recall that cathode-ray tubes produce streams of electrons when a high voltage is applied between electrodes in a vacuum tube, allowing scientists to study the properties of these particles.
3. Recognize that J.J. Thomson used cathode-ray tube experiments in 1897 to discover the electron, identifying it as a negatively charged subatomic particle smaller than atoms.
4. Note that the positron, neutron, and proton were discovered later using different experimental methods: the positron via cosmic rays, the neutron via nuclear reactions, and the proton through studies of hydrogen nuclei.
5. Conclude that the electron is the subatomic particle discovered by researchers working with cathode-ray tubes.