Chapter 271 Gas Conductivity Experiment

The inspiration for the new experiment happened to be given by Lang Zhiwan. Two days ago, he told Zhang Xingjiu that he had received an invitation from the Cavendish Laboratory of Cambridge University and planned to continue his studies under Thomson.

Zhang Xingjiu immediately thought of an important experiment that Thomson would conduct next year, and it was this experiment that won Thomson the 1906 Nobel Prize in Physics.

The investment in this experiment is slightly larger than that of the blackbody radiation experiment. If Zhang Xingjiu had proposed it at the beginning, it would probably have been difficult to obtain permission. But now there is no problem. The success of the blackbody radiation experiment has earned him a certain reputation, and this reputation has also increased his voice. If a suitable experimental plan is put forward, Lippmann will have no reason not to approve it.

Since Maxwell established the electromagnetic field theory, electromagnetism has ushered in great development. Many theories have been quickly transformed into industrial applications. Motors, transformers and high-voltage transmission lines have gradually been used in production, and air leakage has become a problem that needs to be solved urgently.

At the same time, electric lighting also attracted the attention of many scientists, so people competed to study the phenomenon of low-pressure gas power generation.

In 1858, when the German Plucker was studying gas discharge, he noticed a green fluorescence on the wall of the discharge tube facing the cathode, proving that it was caused by some kind of ray emitted from the cathode and hitting the tube wall. This ray was later called cathode ray.

In 1871, British scientist Varley discovered that cathode rays would be deflected in a magnetic field, which was very similar to the behavior of charged particles; Crookes confirmed in his experiment that cathode rays not only travel in a straight line, can be focused, and deflected in a magnetic field, but can also transfer energy and momentum.

Hertz noticed that cathode rays could pass through metal partitions, causing the blocked glass wall to emit a weak fluorescence, a phenomenon that was later studied by his student Leonard.

Thomson at the Cavendish Laboratory had also been studying the phenomenon of gas conductivity, trying to figure out the nature of cathode rays - are they particles or waves? When Roentgen discovered X-rays, Thomson was keenly aware that this discovery might promote his research, so he began to study what X-rays could do in gas conductivity experiments and designed several ingenious experiments.

Now Zhang Xingjiu intercepted his mistake and took out his experimental plan in advance and submitted it to Lippmann for review. Lippmann was a little excited at first, but he was surprised that Zhang Xingjiu took out a new blackbody radiation experimental plan. When he opened it, he couldn't help but frowned, "You have made a breakthrough in the field of blackbody radiation. Why don't you continue along this path, but enter a new field?"

"I don't have any new inspiration for the time being, so I can only continue to use the current plan to repeat the experiments and pay attention to the research of other scholars. If I do this, it will be a waste of time. It happens that I have some new inspiration in the field of gas conductivity. The discovery of X-rays may bring new breakthroughs in this field. This is also a relatively hot field. I think it is worth some attempts." Zhang Xingjiu explained.

By the way, he also complimented her, "I admire your achievements in the field of electricity. As your student, I also want to make breakthroughs in the field of electricity."

Lippmann once invented the capillary potentiometer. If he had applied for a patent for this invention in his own country or other countries, he would have immediately become a millionaire. However, he donated this invention to the French Physical Society.

This is also one of the most important achievements in his life. Now hearing what Zhang Xingjiu said, he naturally felt comfortable and picked up the experimental plan again and read it carefully.

Zhang Xingjiu explained, "Now many scientists are arguing whether cathode rays are particle streams or electromagnetic waves. If you bombard gas with X-rays, if the cathode rays are particle streams, then they will change their direction of movement when they pass through electric and magnetic fields. Otherwise, they are electromagnetic waves."

Lippmann saw that Zhang Xingjiu designed a special cathode ray tube to measure the deflection of cathode rays in an electrostatic field. A pair of metal plates were installed parallel to the channel of the cathode rays and connected to a battery pack.

Through professional judgment, Lippmann believed that the experimental plan was very well designed and had a high probability of success. Looking at the experimental budget attached at the end, although it was a bit high, it was within his acceptable range. He signed the application and said, "I will tell Pierre to purchase the equipment you need as soon as possible. If we can't buy it, we will modify and manufacture it ourselves. I hope you can seize this opportunity."

"Thank you very much. I have full confidence in this experiment." Zhang Xingjiu couldn't help but sigh secretly. Fortunately, France is now in a belle époque and the scientific research budget of universities is very abundant. Otherwise, it might not be passed.

Pierre's ability in experimental management is unquestionable. He quickly prepared for the experiment according to Zhang Xingjiu's needs. Lang Zhiwan also came over excitedly to join in the fun. "Professor Thomson is also studying gas conductivity. I can adapt to it in advance now."

Zhang Xingjiu didn't know what to say for a moment. Soon, they conducted the first experiment, and the results showed that the cathode rays did not deflect at all. Lang Zhiwan believed that this was evidence that cathode rays were electromagnetic waves.

Zhang Xingjiu did not draw a conclusion easily, but proposed a possibility. "Just now, when the battery was connected, the fluorescent spot of the beam shook slightly. Is it because the residual gas molecules dissociated into positive and negative ions under the action of the electric field? The positive ions tended to the negative plate, and the negative ions tended to the positive plate. Before they had time to deflect, they were quickly offset, and the light spot returned to its original position?"

"Well, that's indeed possible." Lang Zhiwan thought for a moment and replied, "Then let's do another experiment to see if we can continue to observe the shaking of the light spot."

The second experiment yielded the same result: the light spot was shaking, but the cathode rays did not deflect at all. So Zhang Xingjiu updated the experimental plan. He spent several days pumping out as much gas as possible from the vacuum tube, and then conducted the experiment again. This time, he obtained a stable deflection.

This result made Professor Lippmann very excited. He came to the laboratory to watch the experiment in person. Zhang Xingjiu also used the method he had just designed to measure the propagation speed of cathode rays in the vacuum tube during the experiment. The result was 1.9×107 cm/s.

He held the data and announced to everyone, "This speed is far lower than the speed of light, so cathode rays cannot be electromagnetic waves."

"That's particle flow?" someone blurted out.

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"No, this experiment only proves that cathode rays are not electromagnetic waves, but it cannot prove that they are particle streams, so we still need new experiments."

(End of this chapter)