The correct option is (a).
Explanation
The discovery of sub-atomic particles was a crucial milestone in understanding the structure of the atom. Experiments involving electrical discharge through gases at low pressure led to the identification of charged particles.
- Statement 1 is Correct: Canal rays were discovered by E. Goldstein in 1886. He performed experiments with a discharge tube containing a perforated cathode and observed a new type of radiation passing through the holes (canals) of the cathode.
- Statement 2 is Incorrect: Canal rays are positively charged radiations, not negatively charged. They are also known as anode rays. In contrast, cathode rays consist of negatively charged particles (electrons).
- Statement 3 is Incorrect: The discovery of canal rays led to the identification of the proton (positively charged sub-atomic particles). It was the study of cathode rays (by J.J. Thomson and others) that led to the discovery of the electron.
Key Takeaway:
Canal rays (anode rays) are streams of positively charged ions discovered by E. Goldstein, which contributed to the discovery of the proton. Electrons were discovered via cathode ray experiments.