Cathode ray

The concept proposed by Joseph John Thomson

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Cathode ray was discovered by German physicist Prucker in 1858 when he used low-voltage gas discharge tube to study gas discharge. In 1876, German physicist Goldstein named this kind of ray cathode ray.^{[2 ]}

1897 Joseph John Thomson According to the trajectory of the cathode ray in the discharge tube under the action of electromagnetic field and magnetic field, the particles in the cathode ray are determined to be negatively charged, and their charge mass ratio is measured, which is the first time in history to discover electrons, 12 years later, American physicists Robert Andrews Millikan The charge of electrons was measured by oil drop experiment.

Chinese name: Cathode ray
Foreign name: cathode ray

Discovery time: 1858
Discoverer: Prucker^{[2 ]}

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brief introduction

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From low pressure gas The discharge tube Electrons from cathode electric field Accelerated Electron flow 。 cathode It can be cold or hot. The electrons are emitted by the field of the applied electric field Positive ion Bombardment or Thermionic emission The process shoots out from the cathode.

application

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Cathode ray is widely used. Oscilloscope tube in electronic oscilloscope and TV Kinescope 、 electron microscope The cathode ray is used to deflect and focus under the action of electromagnetic field, as well as some substances that can be irradiated, such as Zinc sulfide Working in the nature of fluorescence. High speed cathode rays can be generated when hitting some metal targets X-ray , which can be used to study the crystal structure of substances. Cathode ray can also be directly used for cutting melt , welding, etc.

history

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Krux crt Found in Roentgen X-ray So what kind of ray is cathode ray? Cathode ray is a German physicist Julius Plücker It was discovered in the process of low-voltage gas discharge research in 1858. Later, the British physicist Crookes also discovered this kind of ray when he studied the lightning phenomenon in the laboratory. When the air in the glass tube with two electrodes is pumped to a very thin condition, a voltage of several thousand volts is applied between the two electrodes, and a green light flashes on the glass wall opposite the cathode glow However, nothing was seen emitting from the cathode. What the hell is going on here?

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This phenomenon has aroused great interest of many scientists and many experimental studies have been carried out. When an obstacle is placed between the cathode and the opposite glass wall, the shadow of the obstacle will appear on the glass wall; If a rotatable small impeller is placed between them, the small impeller will rotate. It seems that an invisible ray is indeed emitted from the cathode, and it is very similar to a Particle Flow 。 Before people had a clear picture of this kind of ray, they had to call it "cathode ray".

This name was created by a German physicist Goldstein Goldstein.

At that time, there were two completely different opinions on the nature of cathode rays internationally. Most British physicists (e.g Joseph John Thomson ）It is considered that cathode ray is a charged particle stream because it can be deflected by electric or magnetic fields. Thomson and other British physicists also measured that the speed of cathode ray is 2 orders of magnitude smaller than the speed of light. In the early 1890s, German physicists learned from experiments that cathode rays could even penetrate thin Metal foil According to this, they thought that cathode rays could not be particle flow.

At the beginning, British physicist Thomson and German physicist hertz The same experiment was done and the same results were observed. Let's listen to Thomson's own memory of this experience: "My first attempt to deflect the cathode ray was to fix it on the discharge The space between two parallel plates in the tube, and an electric field is added between the parallel metal plates. The result was no sustained deflection. "

For such a same experimental result, Hertz simply and wrongly concluded that the cathode ray is uncharged. But Thomson did not simply engage in it. He carried out more in-depth analysis and thinking, and finally found the problem where the trouble lies 。 In his book Memories and Feelings, he continued to recall that "the reason why deflection did not occur was because of the presence of gas (too high pressure), so the problem to be solved was to obtain a higher vacuum. This is much easier to say than to do."

Thomson continued his in-depth research on cathode rays, and finally completed his world-famous measurement in 1897 Electron specific charge Experiment of^[1] 。

nature

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Cathode ray has two properties, one is perpendicular to the cathode, the other is negative, and always starts from the cathode, and the end point is independent of the anode.

crt

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crt The utility model relates to a cathode ray tube which can reduce the power consumption of a cathode heater. The side heated cathode structure is provided with a metal substrate with a hot electron emission material layer; One end is provided with a base metal holding part, and the inner part is also provided with a tubular sleeve for receiving free electrons of the heater; The diameter of the main part of the heater is larger, and the diameter of the cylinder at the leg side of the heater is smaller, and it is also a special-shaped support of the support sleeve.

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