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8.1 FROM THE UNIVERSE TO THE ATOM

THE ATOM

P81 007

J. Plücker was the first to observe cathode rays within gas discharge tubes. He inferred that the rays were a form of electromagnetic radiation.

(a) Describe a subsequent observation that led other scientists to argue that cathode rays were charged particles.

(b) Identify a potential hazard associated with performing experiments with discharge tube.

(c) Outline a safe work practice which addresses this hazard.

View solution below only after you have completed the answering the question.

Solution

(a) Cathode rays were deflected by electric and magnetic fields negatively charged particles. J.J. Thompson was able to measure q_e/m_e ratio electrons.

(b) To produce an electrical discharge – need very high voltages > 10 000 V.

(c) Make sure that your do not come into contact with the high voltage source.