Question

What were the observations made by E.Goldstein?

Answer 1

He discovered several important properties of cathode rays, which contributed to their later identification as the first subatomic particle, the electron.

He found that cathode rays were emitted perpendicularly from a metal surface, and carried energy.

He attempted to measure their velocity by the Doppler shift of spectral lines in the glow emitted by Crookes tubes.

In 1886, he discovered that tubes with a perforated cathode also emit a glow at the cathode end. Goldstein concluded that in addition to electrons, there is another ray that travels in the opposite direction. Because these latter rays passed through the holes, or channels, in the cathode, Goldstein called them Kanalstrahlen, or canal rays. They are composed of positive ions whose identity depends on the residual gas inside the tube. He is often considered discoverer of protons.

The anode ray with the largest e/m ratio comes from hydrogen gas (H2), and is made of H+ ions. In other words, this ray is made of protons. Goldstein's work with anode rays of H+ was apparently the first observation of the proton, although strictly speaking it might be argued that it was Wien who measured the e/m ratio of the proton and should be credited with its discovery.

Goldstein also used discharge tubes to investigate comets. An object, such as a small ball of glass or iron, placed in the path of cathode rays produces secondary emissions to the sides, flaring outwards in a manner reminiscent of a comet's tail.