Thomson constructed some elegant experiments to find a definitive and comprehensive answer about the nature of cathode rays. They debated whether the rays were waves or particles, as they seemed to exhibit some of the properties of both. Physicists knew that the ray carried a negative charge but were not sure whether the charge could be separated from the ray. However, other researchers, notably Crookes, argued that the focused nature of the beam meant that they had to be particles. With more experimentation, researchers found that the ‘cathode rays’ emitted from the cathode could not move around solid objects and so traveled in straight lines, a property of waves. William Crookes discovered that a tube coated in a fluorescing material at the positive end, would produce a focused ‘dot’ when rays from the electron gun hit it. Later and improved cathode ray experiments found that certain types of glass produced a fluorescent glow at the positive end of the tube. This cathode ray also became known as an ‘electron gun’.
Physicists in the 19th century found out that if they constructed a glass tube with wires inserted in both ends, and pumped out as much of the air as they could, an electric charge passed across the tube from the wires would create a fluorescent glow. Look at any glowing neon sign or any ‘old-fashioned’ television set, and you are looking at the modern descendants of the cathode ray tube. Even without consciously realizing it, most of us are already aware of what a cathode ray tube is.
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