1900: A physics genius wandering around Europe

Chapter 282 Stimulated Radiation! Laser Principle! Verification of the Wave-Particle Duality of Light!
Einstein added another schematic diagram next to the schematic diagram of the two types of electron transitions, spontaneous absorption and spontaneous radiation.

The only difference is that this diagram has one more thing compared to the previous two.

There is a small wavy line with an arrow on the left.

On the right are two smaller segments of the same wavy line.

This means they should be the same thing.

"This wavy arrow represents a quantum of light," Einstein said.

"And the schematic diagram shows the process of collision between light quanta and excited electrons."

"When an electron is already in an excited state, if we hit it with a photon, the electron will not absorb the energy of the photon."

"The electrons get bumped and immediately jump to a lower energy level."

"And during the transition, a photon that is exactly the same as the photon that collided with it will be released."

"The wavelength, polarization and other properties are exactly the same."

"I call this type of electron transition stimulated radiation."

"The energy of the photon used for the collision needs to be equal to the difference between the high energy level and the low energy level."

Then Einstein began to calculate, treating light quanta and electrons as small balls and using mechanical formulas to simulate the calculations.

"I think everyone here will have questions."

"Is there any difference between this so-called stimulated radiation and spontaneous radiation?"

"Because the frequency of the light quanta emitted by the electrons is the same in both processes."

"It just has to do with the energy level difference."

"Yes, there is no difference in the frequency of light quanta."

"But the electromagnetic waves formed by spontaneously radiated light quanta have different phases, polarizations, and propagation directions."

"The electromagnetic waves formed by the photons of stimulated radiation have exactly the same properties as those of the external photons."

"So 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 in 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 related properties.

If two beams of light have the same frequency and a constant phase difference, they are coherent.

Otherwise it is incoherent light, such as incandescent light, sunlight, etc., which are all messy and incoherent light.

Coherent light can undergo constructive interference and destructive interference.

This is what is usually referred to as strengthening or weakening.

The coherent light stimulated by radiation proposed by Einstein not only has the same frequency and phase difference, but also the same polarization direction and propagation direction.

This is a very rare situation.

If his theory could really work, it would be very useful.

Li Qiwei watched Einstein share his theory and was filled with admiration.

In real history, Einstein became a master of physics after publishing the theory of general relativity.

He felt too bored when he had nothing to do.

So I might as well study quantum theory, since it’s so popular right now.

Unexpectedly, this casual research led to a major achievement, namely the so-called stimulated radiation.

This theory is the basis of lasers in later generations.

In this way, a large number of coherent light quanta can be superimposed together and propagate forward without spreading out in all directions.

There's a lot of coherent light in a very small area, so the intensity of the light can be very, very high.

This forms the so-called laser.

Its full name is: light emitted by stimulated atomic radiation.

Laser is another major invention of mankind since the 20th century, following nuclear energy, computers, and semiconductors.

It is called "the fastest knife", "the most accurate ruler", "the brightest light", and plays an important role in countless fields.

The first laser was invented 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 far ahead of experiment.

At this moment, all the bigwigs present were impressed by Einstein's theoretical foundation.

Surprisingly, through theoretical deduction, a completely new way of transition was discovered.

And this theory seems to have great application value.

"As expected, he is the one who published the theory of special relativity with Bruce. This idea is really genius."

"I even think that based on this theory, we may be able to create a light weapon in the future."

"If there is an infinite amount of light superimposed, the energy formed will be extremely terrifying."

"Einstein has come up with something extraordinary."

The big guys really stood high and saw far, and soon discovered the application potential of stimulated radiation.

However, this requires very high precision of the instrument and materials.

With current technology, achieving stimulated radiation and applying it is nothing short of a fantasy.

Therefore, people are mainly concerned about its theoretical value.

At this moment, Bohr breathed a sigh of relief.

"Fortunately, this is just a supplement to the model."

"Instead, it indirectly proves the scalability of the Bohr model."

Bohr was in a very good mood.

Einstein seemed to be challenging Bohr's model and finding its shortcomings.

In fact, it proves the correctness of the Bohr model from another perspective.

It turned out that he was a good friend of my tutor and he was here to help me.

At this time, Li Qiwei also said with admiration: "What a wonderful theory, Einstein."

"If you devote all your energy to the study of quantum theory, you will definitely achieve greater results."

Einstein smiled slightly, and was about to do so.

Because some damn bastard took away his Guangxiang.

This caused Lao Ai to temporarily lose his direction.

He studies whatever is hot at the moment.

"Haha, thank you for the compliment, Bruce."

"I'll think about it carefully."

At this moment, the vast majority of people present were already extremely convinced of quantum theory.

They couldn't imagine what questions the big guys would raise.

At present, there is no problem with quantum theory.

Whether from a theoretical or experimental perspective, it is logically consistent.

We can even create new things based on this theory, such as Einstein's stimulated radiation.

Quantum theory is really good stuff.

Just as Einstein was about to step down, Ridgway announced the question-and-answer session.

Suddenly, a man stood up from the crowd.

Li Qiwei looked at the other person and found that it was an acquaintance, Compton, whom he had met once in the United States.

At this time, Compton's eldest brother Carl quickly lowered his head, with black lines on his forehead.

"Good God, Compton, what are you doing here?"

"Do you have a say here?"

"Even I can only sit here and listen obediently, what are you going to do, go to heaven?"

However, no matter how he pulled Compton's trouser legs, the other party refused to sit down, and it was obvious that he had something to say.

At this time, everyone looked at him, and found that he was a young boy, so they stopped paying attention to him.

Probably a young man who wants to be famous.

I just don't know how strong it is.

However, when Wilson in the front row turned around and saw Compton, he felt his heart skip a beat.

Oops, it's a heart-pounding feeling.

Wilson couldn't understand why this young man gave him a very special feeling.

It's like... it's destined.

He murmured to himself: "It's really strange. I feel like something will definitely happen between me and this guy in the future."

At this moment, Compton was not afraid of the eyes of the big guys in the field, but looked at Li Qiwei firmly.

Li Qiwei was also confused and didn't know what the other party meant.

You are little Karami now, do you have to come up and report? That's impossible. "Oh, it's Compton, do you have any questions?"

Li Qiwei's words surprised everyone. They didn't expect that Bruce actually knew this young man.

It seems that we can't underestimate the other party.

There are no unknown people around Bruce.

Compton said excitedly: "Hello Professor Bruce, hello Professor Einstein."

"Just now, Professor Einstein used the concept of light quanta to predict the existence of stimulated radiation."

"But as far as I know, the physics community has not yet reached a consensus on light quanta."

"Even the idea that light has the dual nature of wave and particle, which you proposed, has not been fully accepted."

“But I personally agree with this view.”

“I think photons exist.”

"Light also has the dual nature of wave and particle."

"So, I would like to ask Professor Bruce, how can we conduct experimental verification?"

“I want to study this direction.”

boom!
Compton's words shocked everyone in the audience.

Then there was a burst of laughter.

Carl lowered his head even lower.

My younger brother is really awesome.

What's the point of your recognition, no matter who you are.

Sure enough, many people began to talk about it.

"It's true that a newborn calf is not afraid of a tiger. Young people should have such courage."

“Set a small goal first, and then work towards it.”

"Haha, I think he is just boasting too much and doesn't know who he is."

"He thinks everyone is Bohr and Qian Wushi."

"Professor Bruce's results are not so easy to verify."

"Millikan became famous just by proving the photoelectric effect, which shows how difficult it is."

Compton was not disappointed by the discussions and doubts of the crowd.

He was just quietly waiting for Li Qiwei's answer.

Facing Compton's question, Li Qiwei had a strange look on his face.

Young man, you are too impatient.

What belongs to you can’t be escaped.

Li Qiwei did not expect that just meeting Compton once would make him pay attention to the wave-particle duality of light in advance.

But he couldn't just say, don't worry, you will definitely know what will happen in the future.

So, Li Qiwei pondered for a while and said with a smile:

"I'm sorry, Compton, but I can't give you any practical advice."

"Otherwise, I would have done it myself a long time ago, so there would be no need for others to do it."

Everyone laughed.

"However, I can suggest a few directions for your reference."

“Since light has the properties of a particle, we must verify it through particle experiments.”

“For example, the collision behavior of light, the change in momentum, and so on.”

"These concepts of kinematics are only possessed by particles."

"If light is also a particle, then it must have these properties as well."

"Of course, it's easier said than done."

"Light is not a solid iron ball. If you want to make it behave like a particle, you need some tricks."

Li Qiwei's words not only made Compton ponder, but also inspired the bigwigs present.

The development of modern physics has exceeded everyone's imagination.

Therefore, light has the dual nature of wave and particle. This incredible situation is no longer something that people dare to object to immediately.

Although no one could imagine how something could be both a wave and a particle.

But it doesn't matter.

Everything depends on experimental data.

If experiments can prove that it is, then it is, and you don't need to worry about what it looks like.

There are so many things that humans cannot imagine.

And Bruce's suggestion is indeed a feasible direction.

But if you just think about it, you will know how precise this experiment is and it is not something that can be successful easily.

The eldest brother Carl was relieved that Compton was doing okay.

Although a little arrogant, it is in line with his age.

When Professor Bruce was young, he was truly crazy.

Compton said thank you and sat down.

Everyone present treated Compton's incident as a minor episode.

However, in the not too distant future, they will be in for a shock.

What an eventful history of physics today’s episode will open.

At this moment, Li Qiwei paused, instantly attracting everyone's attention.

Everyone was concentrating, with impatience written all over their faces.

Next comes the most exciting moment.

Big guy asks a question!

Of course, anyone can ask questions.

But the questions asked are very challenging to one’s personal abilities.

A good question can make people think deeply, but a bad question can only make people laugh.

Li Qiwei smiled and said: "Any theory is perfected in the process of continuous development."

“When a brand new theory emerges, we should neither blindly follow it nor suppress it without reason.”

"Instead, 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 major foundations of modern physics, I must be responsible for it."

“So, everyone is welcome to find out the shortcomings of Bohr’s model from various angles.”

"Let's push quantum theory to its peak together!"

boom!
The venue suddenly erupted into thunderous applause.

Everyone was infected by Li Qiwei's magnanimity.

This is the principle that physics research should follow.

This is also the mindset that a physics master should have.

When a theory is openly discussed, everyone can question it.

It is not like the Newtonian mechanics in the past, where everyone only dared to follow it and did not dare to challenge Newton's authority.

There is only right and wrong in physics, no authority!

Even God is subject to the laws of physics!
After the crowd's emotions and applause gradually calmed down, the first questioner appeared.

It was Professor Michelson.

He smiled and said, "I'm old, and I'm afraid I won't be able to remember the questions later. Let me ask the first question."

"Bohr, do you think it's okay?"

Wow!
The venue suddenly became noisy.

I didn’t expect that the first person to come on stage was a Nobel Prize winner.

This is too exciting.

"Oh my God, this is too much."

"I thought the big guys would take action last."

"It's over. The boss is asking questions first. How dare we ask questions? We're afraid that others will laugh at us."

Bohr, who was sitting in the center of the podium, was also shocked.

That's a Nobel Prize winner.

Moreover, the other party is a veteran in the field of physics and the discoverer of the first dark cloud.

Bohr knew that Michelson's greatest strength was precision optics.

It seems that the other party’s question must be related to spectroscopy.

For a moment, Bohr did not dare to be careless and was ready to go all out.

He took a deep breath and said calmly:
"Of course, Professor Michelson, you are welcome to ask questions."

(End of this chapter)