After waiting for Rutherford to lose his temper, Chen Muwu responded sincerely: "Director, please allow me to finish.
"In our country, there is a famous saying that 'experiment is the only criterion for testing whether a theory is correct or not'."
In order to avoid being favored by the River Crab God, Chen Muwu also thoughtfully changed a few words in it.
“If Millikan hadn’t done precise experiments on the photoelectric effect, and Peter and Blackett had not photographed the trajectory of recoil electrons in the cloud chamber, people would never have believed that light, which has always been considered to be an electromagnetic wave, , in fact, it will also have the properties of particles.
"Similarly, as for the conjecture about whether electrons are a wave, you only need to design an experiment as you said to test whether this conjecture is correct or not.
"The most convenient way to verify whether an electron is a wave is to see whether it can interfere or diffract like light."
Obviously, Rutherford heard what Chen Muwu said: "'Experiment is the only criterion for testing whether a theory is correct or not.' Well...Chen, who said this? What he said is really good! I I thought they could turn this sentence into a sign and hang it in the Cavendish Laboratory."
Chen Muwu’s head was full of black lines, why was Rutherford only interested in this sentence!
"Uh... Director, this is the result of the working people's brainstorming."
Rutherford thought quietly for a while, and even picked up Chen Muwu's pen and scratch paper from the table, and made a few calculations on them.
Then he continued to ask: "If electrons are really a wave, according to the formula you gave, even an electron with an energy of only one electron volt would have a corresponding wavelength of only about one nanometer.
"This value is far smaller than the wavelength of visible light, so it cannot easily obtain interference or diffraction patterns after passing through a double slit or a single slit like visible light... Wait!
"Looking at it this way, the wavelength of an electron with an energy of one electron volt should be in the same order of magnitude as the wavelength of X-rays. In other words, it is completely possible to allow electrons to be incident into the crystal just like the X-ray crystal diffraction experiment. Look at the photographic film to see if there is a diffraction pattern to detect whether electrons are a kind of wave?"
Seeing the calm expression on Chen Muwu's face as he sat firmly on the Diaoyutai, Rutherford finally realized: "Chen, have you already thought about this experiment?"
Chen Muwu smiled and said nothing, then nodded.
"I knew it," Rutherford, who was getting more and more excited, even put his hands on Chen Muwu's shoulders, "I knew it, Chen, you are a genius!"
After all, he was still a young man in his twenties, and Rutherford's praise made Chen Muwu feel a little elated.
But before the latter had time to be happy, the former poured a ladle of cold water on his head.
"It's a pity, Chen, I'm sorry," Rutherford, who had calmed down after smoking a pack of cigarettes, changed the subject, "I'm afraid I won't let you do this experiment. I mean, at least in the recent period, you I can’t do this experiment yet.”
Um?
Hearing the word "sorry", Chen Muwu felt something was wrong. When he heard the full content of Rutherford's words, Chen Muwu felt that his head suddenly became bigger.
"Director, why is this?"
His tone unconsciously contained anxiety.
Rutherford said with a look of regret: "To be honest, Chen, although you talked about electron fluctuations in a very colorful way, the new electron theory you proposed, or it should be more appropriately called a conjecture, did not convince me. I am not convinced." I am pessimistic about whether this experiment will be successful and have little confidence.
"Can't I have to arrange a new experiment every time you come up with a theory?
"You know, doing experiments can't be done by just having a flash of inspiration and patting your head. If you want to do an experiment well, you must be fully prepared and have the persistence to endure failure again and again. And the strong spirit of repeating the previous futility again and again.
"Furthermore, the electron diffraction experiment you mentioned is different from the previous gamma ray scattering experiment. There are too many aspects that require money."
"But," Chen Muwu still wanted to argue for himself. He really didn't want the electron diffraction experiment to be aborted. "But director, do you need any special equipment to do this experiment? I only need one to launch the experiment." An electron beam cathode ray tube, an accelerating electric field, then a metal crystal, and finally a few photosensitive films are all it takes!”
But Rutherford still shook his head stubbornly: "Chen, you have committed a common problem among people your age, that is, you are too young and too naive.
"Do you think that doing this experiment is similar to doing X-ray crystal scattering? You only need to prepare the radiation source, crystal, and photographic film, and put them in the corresponding positions to get the corresponding diffraction pattern?"
Chen Muwu nodded.
“I thought the same way at first, so I thought you came up with a genius idea.
"However, after calming down for a while, I thought that electrons are not gamma rays after all. Their penetrating power is not strong and cannot spread unimpeded in the air like electromagnetic waves. It can easily interact with the electromagnetic waves in the air. Molecules collide and ionize, which can have a great impact on the experiment.
"However, in order to do your experiment, the electron beam, the diffraction crystal and the photographic film must all be in a high vacuum state, which is indispensable. And this vacuum level cannot be reached in our laboratory now.
"Cavendish's current vacuum pump is still the Sprenger mercury pump made by Sir Thomson and Aston more than ten years ago. The degree of vacuum it can provide is far from allowing your electrons to obtain enough The free path is so long that it can be accelerated from the cathode emission point by the potential difference and diffracted by the crystal, and finally hit the photographic film.
“I heard that General Electric Company in the United States invented a more technologically advanced vacuum pump, but unfortunately, we can’t afford it!
"If we are as rich as the Yankees, or even half as rich as them, then I will never refuse your experimental proposal.
"But it's almost the end of the year, and the fall semester of the new school year is about to start. Several new students will be admitted to the laboratory. Cavendish really doesn't have much money on its books to allow you to buy that vacuum pump. Experimenting."
As soon as money was mentioned, the expression on Rutherford's face became more and more helpless.
From the experimental environment and experimental equipment, Chen Muwu has seen the poverty of the Cavendish Laboratory.
But he didn't expect that the actual situation was even poorer than what he saw.
With a yearly budget of more than 9,000 pounds, it starts to be calculated carefully in August. No wonder Rutherford said, "Because we have no money, we have to think."
It seems that this is not because he is humble, but because he really has no money!
well!
…
After Rutherford left the conference room, Chen Muwu gradually calmed down.
The director's words were unreasonable, and every word he said was factual.
Regarding electron diffraction, Chen Muwu only saw the diffraction patterns of Davidson, Gemo and Thomson in the textbook when he was studying quantum mechanics, but he did not learn in detail how these two experiments were done. from.
Therefore, he took it for granted and regarded electrons as electromagnetic waves like X-rays. He did not consider that when electrons are exposed to the air, they will collide with air molecules and produce ionization, which will affect the experimental results.
Ginger is still very old, and it only took a few minutes of thinking time for Rutherford to point out Chen Muwu's problem to the point.
After his prodding, Chen Muwu suddenly realized that he had indeed thought too little.
He felt that since he traveled through time, everything had gone too smoothly, so he couldn't help but feel a little dizzy lately.
Being scolded by Rutherford also sounded a warning to Chen Muwu, that is, even if he knows the future scientific development, he must guard against arrogance, impetuosity and be down-to-earth in scientific research.
In the original space and time, after de Broglie proposed the concept of matter waves, when Langevin asked him how to verify the existence of matter waves, de Broglie also proposed the electron diffraction experiment like Chen Muwu.
But first, people think that this French aristocrat is just a newbie in physics who has not even obtained a doctorate and is not famous. His statement is too unreasonable. Electrons are electrons and cannot be waves.
The second reason is that it was really difficult to achieve a vacuum that allowed electrons to successfully diffract in crystals on the European continent at that time.
So even though de Broglie had given the experimental method of crystal diffraction, no one was willing to do this experiment.
Even in the private laboratory of his brother, Maurice de Broglie, the sixth Duke of de Broglie, no one was willing to pay attention to the nonsense of this little prince.
Colin Davison and Lester Germer, who were the first to discover the existence of crystal diffraction in electron beams, had actually begun to conduct related experiments before de Broglie proposed the concept of matter waves in 1924.
However, their experiment was not initially intended to prove the existence of matter waves in advance, but simply to detect the impact of electron bombardment on metals.
During this period, although Davidson published several experimental results, he had no idea that de Broglie in Europe had already proposed the concept of matter waves.
It wasn't until 1926 that Davidson got married again and took his second wife to the UK for their honeymoon. By chance, he attended a local physics conference and found that Born was holding experimental data he had published a few years ago. After talking specifically about de Broglie's matter waves, Davidson realized that there was a concept of matter waves.
It was also after that that Davidson, who returned to the United States, and Thomson Jr., who attended the meeting, used low-speed electrons and high-speed electrons respectively in their respective laboratories to design electron beam crystal diffraction that could verify the material wave theory. experiments and finally achieved positive experimental results.
If Davidson had not done the experiment of electron bombardment on a metal surface by mistake, and Born happened to see the results of this experiment and announced it at the meeting, then the experimental verification of matter waves might still be far away.
This is enough to show how unpopular de Broglie's matter wave theory was when it was first proposed.
It took eighteen or nineteen years for the photon theory to be proposed and finally confirmed to exist through experimental verification of the photoelectric effect and the Compton effect.
People have just begun to believe that light, which has long been thought to be a wave, is also a particle.
Now I want them to believe that the electron, which is originally a particle, is also a wave. Of course, there will be strong resistance.
Although Rutherford reprimanded Chen Muwu and then rejected his request for an experiment, it is estimated that compared with the cynicism that de Broglie received at the beginning, the attitude of the director of the Cavendish experiment can be regarded as Very pleasant!
Happy April Fools' Day!
Please support me in the new month!
(End of chapter)
