1900: A physics genius wandering around Europe

Chapter 540: In the wave-particle duality of light, does the wave refer to electromagnetic wave or probability wave?
The research content of Cockcroft and others deeply shocked everyone present.

With the continuous improvement of quantum mechanics, the development of nuclear physics has a solid theoretical foundation and its speed will surely advance by leaps and bounds.

At this time, Li Qiwei suddenly said to Irena beside him:
"Irena, since there are artificial nuclear reactions, is there artificial radioactivity?"

"Your parents discovered the natural radioactivity of radium. So is it possible to create radioactivity artificially?"

boom!
There was a sudden thunder explosion in Irena's mind!

This idea is incredible!
Radiology is nearly thirty years old.

In 1896, Becquerel first discovered the radioactivity of uranium, opening up the field of radiology.

In 1898, her parents, the Curies, discovered radium and polonium, which are even more radioactive.

To date, physicists have discovered dozens of different naturally occurring radioactive elements.

But no one had ever thought of creating radioactivity artificially.

Since radioactivity is the spontaneous behavior of atoms, how can it be controlled artificially?
Irena asked with little confidence:

"Professor, is this possible?"

Li Qiwei smiled slightly, looking mysterious, and said:
"How do you know it's impossible if you haven't tried it?"

"This is a topic that suddenly occurred to me. If you are interested, you can try it."

Irena's beautiful eyes burst into a bright light.

If she can really achieve artificial radioactivity, it will definitely bring radiology to a whole new level!

Even surpassing her parents and leading the times!
She had already begun to daydream.

Li Qiwei found Irena's silly look a little funny.

He sighed in his heart:
"The turbulent nuclear age is coming!"

After the students’ presentations, it was Wilson’s turn to share the results of his cloud chamber research.

He walked to the front confidently and calmly, looking at the crowd, his thoughts flying.

Once upon a time, his cloud chamber was just a simple instrument that could observe microscopic particles.

But with the rise of modern physics, cloud chambers have become increasingly important and indispensable.

And all of this originated from that beautiful encounter.

"Now, I will give you a problem. If anyone can solve it within a month, I will give him full marks for this course, and he will not have to come to class anymore."

"."

"By the way, Dr. Wilson, I think the name 'Particle Observer' is not nice. How about calling it 'Cloud Chamber'?"

"Bruce, you are amazing!"

"."

The memories came flooding back to Wilson, and a smile formed on his lips.

He gave Li Qiwei a gentle look, causing the latter to instantly get goosebumps.

Soon, Wilson said seriously:

“The birth of the cloud chamber actually originated from the study of X-rays.”

"X-rays were first discovered by the late Professor Roentgen in 1895."

"When the news reached Britain, Professor Thomson at the time was very interested in this new physical phenomenon."

"He began to study the electrical conductivity of air after exposure to X-rays."

"He proposed the famous gas ionization theory hypothesis, which states that when air is irradiated by X-rays, ionization will occur."

"Then Professor Thomson asked me to do an experiment to verify this conjecture."

“I was inspired by the reflection of sunlight on clouds and came up with the idea for the Cloud Room.”

"The so-called cloud chamber is a sealed metal container filled with a certain amount of water vapor. It looks like smoke, hence the name."

"Besides, this name was given to me by Professor Bruce."

"That was a long time ago. Many of you here may not have been born yet."

Everyone was surprised.

I didn’t expect that the Cloud Chamber was also related to Professor Bruce.

"If we assume that the air is ionized, then charged particles will be formed."

"These charged particles will form a core, attracting water vapor in the air and turning it into water droplets."

"According to this principle, if water droplets appear when I irradiate the air with X-rays, it proves that the gas ionization theory is correct."

"In the end, the experiment went smoothly. When the X-rays were turned on to irradiate the cloud chamber, water droplets immediately appeared inside."

When everyone heard this, they all marveled at Professor Wilson's brilliant ideas.

Such beautiful results can be achieved using such simple instruments.

Compared to Cockcroft's particle accelerator, the cloud chamber was ridiculously simple.

But its approach to solving problems is very clever, unlike a particle accelerator that relies on brute force to create miracles.

Each has advantages and disadvantages.

Li Qiwei also recalled his memories. During that time, he helped Lao Wei a lot.

At this point, Wilson continued:
“The success of the cloud chamber sparked my interest in it.”

“I wondered if we could develop some new features based on the original one?”

"Since ionized air can condense water droplets, can all charged particles condense water droplets?"

"Through a lot of experiments, I finally figured out the current method for different kinds of charged particles."

"Thus, the cloud chamber became an instrument for studying microscopic charged particles, which greatly expanded its scope of use."

"Later, I added a photo-taking function to the cloud chamber, making it more practical."

"Then, as physics continued to develop, cloud chambers gradually became known to physicists."

“It’s getting more and more precise, and it’s getting more and more capable.”

"Using it, we can accurately measure the speed, charge, type and other parameters of particles."

"."

Everyone listened with great interest.

Understanding the transformation process of the cloud chamber from beginning to end can help them use the cloud chamber more deeply.

Finally, Wilson got to Heisenberg's cloud chamber trajectory problem.

"Everyone, please take a look."

"This is a picture of the electron's motion trajectory that I took using the highest-resolution cloud chamber available."

"After magnifying it 100 times, you can clearly see that the electron's path is indeed discontinuous."

"This is in perfect agreement with Professor Bruce's judgment, and it also proves the correctness of matrix mechanics."

Wow!
Everyone was amazed.

As expected, Professor Wilson’s cloud chamber photos are the most authentic, clear and beautiful.

After seeing this, Heisenberg smiled widely.

"My matrix mechanics are flawless indeed."

At this moment, he suddenly saw Professor Bruce staring at the photo, thoughtfully.

The other person's fingers tapped rhythmically on the chair handle.

Heisenberg was puzzled.

The electron track photos in front of us can be said to perfectly explain the problem.

"So what is Professor Bruce thinking about?"

Finally, Wilson suddenly smiled and said:

"Unfortunately, my cloud chamber is powerless to help with Professor Bruce's probability wave theory."

"Quantum mechanics is such a high-level theory that a clumsy person like me cannot deeply participate in it."

"thank you all."

Everyone laughed and then applauded.

Wilson's report allowed everyone to see the style of the experimental master.

That's a very different style from that of a theoretical physicist.

At this time, Rutherford said: "Now it's time for free discussion in the salon."

“Everyone can discuss any academic topic of interest.”

Soon, the room became lively.

People either stand and walk around, or sit, or talk in groups of two or three, or throw out a topic for everyone to discuss.

Everyone enjoyed the food while discussing the most cutting-edge academic issues.

"Dr. Davidson, how did you come up with the idea of ​​using a nickel target for your experiment?"

"Mr. Cockcroft, how do you ensure a smooth transition of the electric field in your particle accelerator?"

"."

In such a relaxed environment, it is easier to generate many wild inspirations.

At this time, Dirac, who had always been taciturn and rather withdrawn, suddenly raised a question that attracted everyone's interest.

"In the wave-particle duality of light, does the wave refer to the electromagnetic wave or the probability wave?"

After completing his doctoral thesis, Dirac devoted most of his energy to the study of quantum mechanics.

Especially the introduction of probability waves made him extremely obsessed with this mysterious theory.

After everyone thought about it carefully, they found that the question became more and more interesting.

With the proof of the existence of matter waves by Davisson and Thomson Jr., wave-particle duality has become a consensus in the physics community.

Many experimental results have proved this point.

The wave-particle duality of light was proposed long before the matter wave theory.

There is no doubt that the essence of light is electromagnetic waves.

Electromagnetic waves are divided into gamma rays, X-rays, infrared rays, visible light, ultraviolet rays, microwaves and other types according to their wavelength or frequency.

When people usually say the word "light", they usually refer specifically to "visible light", which is electromagnetic waves with a wavelength between 380nm and 780nm.

That is the seven colors of light that everyone is familiar with: red, orange, yellow, green, cyan, blue and violet.

Soon, everyone expressed their opinions on this issue.

Fowler, Dirac's mentor, thought for a while and said:
"For hundreds of years, the wave-particle debate, the evidence and theories provided by the wave school are all based on the traditional mechanical wave theory."

"At that time, physicists did not fully understand the nature of light and could only compare its wave nature to mechanical waves."

"With Maxwell's unification of electromagnetic light and Hertz's proof of the existence of electromagnetic waves, physicists finally figured out that the essence of light is electromagnetic waves."

“Therefore, the so-called wave-particle dispute is actually the dispute between electromagnetic waves and particles.”

“Moreover, when Professor Bruce first proposed the wave-particle duality of light, there was no concept of probability waves.”

"From these aspects, in the wave-particle duality of light, the wave should refer to the electromagnetic wave."

After hearing this, everyone nodded slightly.

Fowler's analysis is very pertinent, and he answers this question from the history of light research.

But then he turned around and said:

"However, this Dirac question is an interesting one."

“After Professor Bruce proposed the concept of photons, he explained that photons are microscopic particles like electrons, protons and other particles.”

"It's just that electrons have mass, and photons don't."

"But no matter what, as long as it is a microscopic particle, it must satisfy de Broglie's matter wave theory."

"From this perspective, photons should have the properties of probability waves."

"Analyzed in this way, light seems to be both an electromagnetic wave and a probability wave."

“This is really an incredible phenomenon.”

Everyone exclaimed!
The light is indeed a bit strange.

Electromagnetic waves and probability waves are obviously two waves with completely different natures. How can light have both of them?

Existing theories do not provide a convincing explanation.

At this time, Heisenberg frowned, as if he had grasped something key.

"I think the words and concepts of 'light' and 'photon' should not be confused."

“Light is a macroscopic phenomenon. It is an electromagnetic wave formed when periodically changing electric and magnetic fields move at the speed of light.”

"And [photon] refers to the basic unit of light, which is a microscopic concept."

"The energy of electromagnetic waves is transmitted in the form of photons."

"When we talk about the wave-particle duality of light, the light here refers to macroscopic light."

"So, its wave nature should specifically refer to electromagnetic waves."

"But [photons] themselves, as microscopic particles, also have the properties of probability waves."

hiss!
Heisenberg and Fowler's analysis made the problem even more confusing.

The uniqueness of light is once again revealed to everyone.

Originally, everyone thought that Professor Bruce’s proposal of the wave-particle duality of light had resolved hundreds of years of debate.

But with the introduction of probability waves, things don't seem that simple.

However, Pauli thought differently.

“I think that’s normal.”

"Take water waves as an example. [Light] is [water waves], and [photons] are [water molecules]."

"Water waves themselves are made up of countless water molecules."

"In a single water molecule, both the hydrogen and oxygen atoms have the properties of probability waves."

"But they can still form definite mechanical waves like water waves."

Dirac countered:

"No, that's not the right analogy."

"It should be that [light] is equivalent to [water waves], and [photons] are equivalent to [one unit of water waves]."

“But even if it’s a single-unit water wave, it’s still a mechanical wave, not a probability wave.”

Pauli disagreed.

"Bullshit!"

Irena said:
“I think Dirac is right.”

At this point, Heisenberg added:

“That creates a problem.”

“Since [photons] have the properties of probability waves, then it stands to reason that their position in space and time should also be probabilistic.”

"But why does light have a definite straight trajectory after a large number of photons form it?"

"Why doesn't it just diffuse randomly throughout the universe and time and space like electrons?"

Everyone was shocked.

"Yeah, why?"

Little Bragg is an expert in electromagnetism. He said:
“Maybe it’s a mathematical problem, where the statistical behavior of a large number of photons cancels out the probabilistic randomness of a single photon.”

In real history, after Rutherford's death in 1937, Bragg Jr. became the fifth director of Cavendish.

After he came to power, he gave up his area of ​​expertise and instead vigorously developed marginal disciplines such as solid state physics, biophysics, and astrophysics, opening up new research directions for the laboratory.

After listening to his explanation, everyone nodded.

Pauli immediately said:

"This is the same reason why a single atom has the properties of a probability wave, but a solid composed of a large number of atoms can produce mechanical vibration waves."

"Probability waves are also subject to the constraints of the wave equation."

Soon, this group of young people began to have a heated discussion.

The process was wonderful and everyone watched it with great interest.

At this moment, Heisenberg suddenly discovered that Professor Bruce had been sitting there, as if thinking about something quietly.

"I always feel like he's going to pretend to be awesome and come up with some amazing theory again."

(End of this chapter)