Chapter 4, Problem 68A

Interpretation Introduction

Interpretation : The characteristics of cathode rays that led to Thomson to conclude that the rays consisted of negatively charged particles is to be described.

Concept Introduction : Thomson was the person behind the discovery of electrons that revolve around the nucleus. Thomson called his model as a plum-pudding model, in which the electrons were struck into a bulk of positive charge.

Answer to Problem 68A

The cathode rays are deflected and drawn towards positively charged plates which led Thomson to conclude that the rays consisted of negatively charged particles.

Explanation of Solution

Thomson conducted tests with the flow of an electric current through low-pressure gases.

He contained the gases in glass tubes with electrodes—metal disks—fitted at both ends.

The anode electrode was the only electrode to positively charge.

The cathode, the other electrode, developed a negative charge. A glowing beam, or cathode ray, was produced as a result and moved from the cathode to the anode.

Thomson discovered that electrically charged metal plates can deflect a cathode ray.

The cathode ray is drawn to positively charged plates while being repelled by negatively charged plates.