Chapter 283 Stimulated Radiation! Laser principle! Verify the wave-particle duality of light!
Einstein added another schematic diagram next to the schematic diagrams of the two transition modes of electron spontaneous absorption and spontaneous emission.
It’s just that compared to the previous two, this diagram has one more thing.
There is a small wavy line with an arrow on the left.
On the right are two small sections of the same wavy line.
This means they should be the same thing.
Einstein said: "This wavy arrow represents a light quantum."
"The schematic diagram represents the process of collision between a light quantum and an excited state electron."
"When the electron is already in an excited state, if we hit the electron with a light quantum at this time, the electron will not absorb the energy of this light quantum."
"The electron will be collided and immediately move to a lower energy level Jump.”
"And during the transition, a photon of light that is exactly the same as the photon that collides with it will be released."
"The wavelength, polarization and other properties are exactly the same."
"This way of electronic transition , I call it [stimulated radiation]”
“The energy of the photon used for impact needs to be equal to the difference between the high energy level and the low energy level”
Then Einstein began. For calculations, consider light quanta and electrons as small balls, and use mechanical formulas to perform simulation calculations.
"I think everyone here must have questions."
"What is the difference between this so-called stimulated emission and spontaneous emission?"
"Because in both processes, electrons emit The frequency of the light quanta is the same."
"It is only related to the energy level difference."
"Yes, there is no difference in the frequency of the light quanta."
"But the electromagnetic waves formed by spontaneously emitted light quanta have different phases, polarizations, and propagation directions."
"The electromagnetic waves formed by stimulated emission of light quanta have exactly the same properties as those of external light quanta."< br>
“Therefore the electromagnetic waves emitted by stimulated radiation are coherent.”
Wow!
When it comes to coherence, even the students present can understand it.
Because coherence is the most basic concept of wave mechanics.
The so-called coherence means mutual interference.
If two or more waves have the same frequency and a constant phase difference, then they are coherent waves.
Electromagnetic waves are also waves.
So there are also related properties.
If two beams of light have the same frequency and a constant phase difference, then they are coherent lights.
Otherwise, it is incoherent light, such as incandescent light, sunlight, etc., which are all messy incoherent light.
Coherent light can undergo constructive interference and destructive interference.
This is commonly referred to as strengthening or weakening.
The stimulated emission of coherent light proposed by Einstein not only has the same frequency and phase difference, but also the polarization direction and propagation direction.
This is a very rare situation.
If his theory can really be realized, it will be of great use.
Watching Einstein finish sharing his theory, Li Qiwei was filled with admiration.
In real history, after Einstein published the general theory of relativity, he became a master of physics.
He felt too bored with nothing to do.
So let’s just study quantum theory, which is so popular now.
Unexpectedly, this random research led to a major result, which is the so-called stimulated radiation.
This theory is the basis of later generations of lasers.
In this way, large numbers of coherent light quanta can be superimposed and propagate forward without spreading in all directions.
In a very small area, there is a lot of coherent light, so the intensity of the light will be very, very high.
This creates what is called a laser.
Its full name is: light stimulated emission of atoms.
Laser is another major invention of mankind since the 20th century, after nuclear energy, computers, and semiconductors.
It is called "the fastest knife", "the most accurate ruler" and "the brightest light," and plays an important role in countless fields.
The first laser invented by mankind was in 1960.
Its principle was proposed by Einstein in 1916.
Einstein was simply more than forty years ahead of his time.
This is also an example of theory being far ahead of experiment.
At this moment, the big guys present were impressed by Einstein's theoretical foundation.
Using theoretical derivation, a brand new way of transition was discovered.
And this theory seems to have great application value.
“As expected, he is the one who published the special theory of relativity with Bruce. This idea is indeed genius.”
“I even wonder if a light weapon will be created in the future based on this theory. ."
"If there is infinite light superimposed, the energy formed will be very terrifying."
"Einstein has created something extraordinary."
As expected, the big guys stood high and saw far, and soon discovered the application potential of stimulated radiation.
However, this requires very high precision and material requirements for the instrument.
With current technology, it is impossible to realize stimulated radiation and apply it.
Therefore, everyone mainly focuses on its theoretical value.
At this moment, Bohr breathed a sigh of relief.
"Fortunately, this is just a supplement to the model."
"On the contrary, it proves the scalability of Bohr's model in disguise."
Bohr was in a good mood.
Einstein seemed to challenge Bohr's model and find its shortcomings.
In fact, it proves the correctness of Bohr's model from another perspective.
As expected, he was a good friend of my mentor, and he was here to help me.
At this time, Li Qiwei also said with admiration: "What a wonderful theory, Einstein."
"If you fully participate in the study of quantum theory, you will definitely achieve greater success. Results."
Einstein smiled slightly, and he was about to do this.
Because some damn person took away his prime ministership.
As a result, Lao Ai's classmate temporarily lost his direction.
A hammer in the east and a mallet in the west, whatever is hot to study.
"Haha, thank you for the compliment, Bruce."
"I will think about it carefully."
At this moment, the vast majority of people present have no idea about quantum theory. Already extremely convinced.
They could not imagine what questions those big guys would raise to question.
At present, there are no problems with quantum theory.
Whether it is from a theoretical or experimental perspective, it is logically self-consistent.
It is even possible to create completely new things based on this theory, such as Einstein's stimulated radiation.
Quantum theory is really a good thing.
Just as Einstein was about to step down, Li Qiwei announced that he would enter the question period.
Suddenly, a man stood up in the crowd.
Li Qiwei looked at the other person, he was still an acquaintance, it was Compton whom he had met once in the United States.
At this time, Compton's eldest brother Carl quickly lowered his head, and black lines appeared on his forehead.
“Jesus, Compton, you’re just fooling around.”
"Do you have the right to speak here?"
"Even I can only sit here and listen to the lecture. What do you want to do, go to heaven?"
However, no matter he Why did Compton tug on his trouser leg, but the other party refused to sit down, so he obviously had something to say.
At this time, everyone looked at him and found that he was a young boy, so they stopped paying attention.
Probably a young man who wants to be famous.
I just don’t know what the strength is.
However, Wilson in the front row turned his head and saw Compton, and suddenly felt his heart skip a beat.
Oops, it’s a heart-pounding feeling.
Wilson couldn't understand why this young man gave him such a special feeling.
It’s like. It’s like destiny.
He murmured to himself: "It's really strange. I feel that something will happen with this young man in the future."
At this moment, Compton was not afraid of the eyes of the big guys in the field, but was determined to He looked at Li Qiwei.
Li Qiwei was also confused, not knowing what the other party meant.
You are little Karami now. Do you have to come up and report? It’s impossible. "Oh, it's Compton, what's your problem?"
Li Qiwei's words surprised everyone. They didn't expect that Bruce actually knew this young man.
It seems that we cannot underestimate the other party.
There are no unknown people around Bruce.
Compton said excitedly: "Hello, Professor Bruce, hello Professor Einstein."
"Professor Einstein just used the concept of light quanta to predict the phenomenon of stimulated emission of radiation. exists.”
"But as far as I know, the current physics community has not yet reached a unified opinion on light quantum."
"Even the view that light has wave-particle duality proposed by you, Professor Bruce, has not been fully recognized."< br>
“But I personally agree with this point of view.”
“I think light quanta exists.”
“Light also has wave-particle duality.”
"So, I want to ask Professor Bruce, how to do experimental verification?"
"I want to study this direction."
Boom!
Compton’s words shocked everyone in the audience.
Immediately bursts into laughter.
Karl's head was buried lower.
My younger brother is really awesome.
What is your identity and what is the use of your recognition.
As expected, many people started talking about it.
“Sure enough, a newborn calf is not afraid of tigers. Young people should have such courage.”
"Set a small goal first, and then work hard towards it."
"Haha, I think he is exaggerating and can't recognize himself."
"He thinks everyone is the same Bohr and Master Qian."
"Professor Bruce's results are so easy to verify."
"Millikan has become famous just by verifying the photoelectric effect. It shows how difficult it is.”
Compton was not disappointed by the public's comments and doubts.
He was just waiting quietly for Li Qiwei's answer.
Faced with Compton's question, Li Qiwei looked strange.
Young man, you are too impatient.
It's yours, you can't even run away.
Li Qiwei did not expect that just one meeting with Compton would lead him to pay attention to the wave-particle duality of light in advance.
However, he can't just say, don't worry, you will definitely know in the future.
So, Li Qiwei thought for a while and said with a smile:
"Sorry, Compton, I can't give you any feasible suggestions."
"Otherwise , I have already done it myself, so how could it be someone else’s turn?”
Everyone laughed.
“However, I can suggest a few directions for your reference.”
“Since light has the characteristics of particles, it must be verified through particle experiments.”
“For example, the collision behavior of light, momentum changes, etc.”
“These kinematic concepts are only possessed by particles.”
"If light is also a particle, then it must also have these properties."
"Of course, it is very simple to say, but it will be very complicated to do."
"Light is not a solid iron ball. If you want to It shows particle nature, which requires some skills.”
Li Qiwei’s words not only made Compton think deeply, but also inspired the big guys present.
The development of modern physics has exceeded everyone's imagination.
Therefore, light has wave-particle duality. This incredible situation, no one dares to object immediately.
Although no one can imagine how something can be both a wave and a particle.
But it doesn’t matter.
Everything depends on experimental data.
If the experiment can prove that it is, then it is, you don’t need to worry about what it looks like.
There are too many things that humans cannot imagine.
And Bruce's suggestion is indeed a feasible direction.
But just thinking about it briefly, you will know how precise this experiment is, and it cannot be succeeded casually.
The eldest brother Carl breathed a sigh of relief, Compton's performance was okay.
Although he is a little arrogant, it is consistent with his age.
When Professor Bruce was young, he was truly crazy.
After Compton said thank you, he sat down.
Everyone present regarded Compton's incident as a minor incident.
However, in the near future, they will be shocked.
Today’s episode will open up a magnificent history of physics.
At this time, Li Qiwei paused his voice, instantly attracting everyone's attention.
Everyone was attentive, and the look of impatience was written on their faces.
The most exciting moment comes next.
Big question!
Of course, anyone can ask questions.
It’s just that asking questions is a great test of personal ability.
A good question can make people think deeply, but a bad question can only make people laugh.
Li Qiwei said with a smile: "Any theory is perfected through continuous development."
"When a brand-new theory appears, we can neither blindly pursue it nor suppress it for no reason. . ”
“But we should study this theory with the most scientific and rigorous attitude. ”
“This is also the ultimate goal of this conference.”
“Since I dare to say that quantum theory is the two foundations of modern physics, then I must be responsible for it.”
“ Therefore, everyone is welcome to find out the shortcomings of Bohr’s model from various angles.”
“Let’s push quantum theory to its peak!”
Boom!
The venue suddenly burst into earth-shattering applause.
Everyone was infected by Li Qiwei’s great spirit.
This is the principle that physics research should have.
It is also the mind that a physics master should have.
When a theory is openly discussed, everyone can question it.
Instead of being like the previous Newtonian mechanics, everyone only dared to regard it as a standard and did not dare to challenge Newton's authority.
Physics has only right and wrong, no authority!
Even God must be included in the laws of physics!
After the crowd's emotions and applause gradually calmed down, the first questioner appeared.
It is Professor Michelson.
I saw him smiling and saying: "I'm getting older and I'm afraid I won't be able to remember the questions later. Let me be the first to ask."
"Bohr, do you think that's okay?"
Wow!
The venue suddenly became commotion.
I didn’t expect that the Nobel Prize winner would be the one who came on stage at the beginning.
This is too exciting.
“My God, this is too exaggerated.”
“I thought the big guys would take action last.”
“It’s over, the big guys are first. How dare we ask questions? We might make others laugh."
Bohr in the middle of the podium was also surprised.
That's a Nobel Prize winner.
And the other party is also an old-timer in the world of physics, the discoverer of the first dark cloud.
Bohr knew that Michelson was best at precision optics.
It seems that the other party's problem must be related to spectroscopy.
For a time, Bohr did not dare to be careless and prepared to go all out.
He took a deep breath and said calmly:
"Of course, Professor Michelson, your questions are welcome."
(End of this chapter)