Due to the large number of experts and scholars at the scene, although the students in the audience wanted to ask some personal questions, they still did not dare to ask them.

After a few decent questions, a very man-looking boy took the microphone,

"Hello Mr. Han, just now you used the Fermat principle in optics to derive Snell's law, so how to prove Fermat's principle with Maxwell's equations?

Thanks, my question is finished. ”

As soon as the boy finished speaking, dozens of strange eyes from the audience focused on him.

At the same time, a professor at SUSTech on the stage looked very unnatural. He covered his mouth and coughed, and then looked at the very manly boy with a faint look.

Han Yi hesitated slightly.

The knowledge on the blackboard, he didn't cheat, it was completely real.

After all, I've been doing research for so long, and if I can't even explain the principle, it's too wasteful.

However, the boys in the audience asked a little biased.

It is common to use Maxwell's equations to prove the laws of refraction and reflection, and it is the first time I have heard of Fermat's principle.

He took a sip of the teacup and summoned Surel in his mind, and in an instant, a multi-minute solution to the problem appeared in front of him.

After putting down the teacup, Han Yi said with a smile: "Fermat's principle is essentially closely related to the optical Mo Peidu principle;

Thus, from Maxwell's equations, the Fermat principle is inferred;

Under the passive assumption, the heterogeneous medium boundary uses Stokes' theorem, and the law of refraction is known from Maxwell's equations in integral form.

Then let's set one point on each side of the dielectric surface, α1, β2, if the passing point of the dielectric surface is α and β, then the full optical path time can be obtained v=c/n,

The law of refraction obtained by the derivative satisfies Maxwell's equations;

I won't go into the specific values, but the time to derive Fermat's principle should be the shortest path. ”

The value is stinky and long, and it seems too pretentious to say it directly, so Han Yi kept his hand.

It didn't matter what he kept, the boy in the audience was dumbfounded.

This is what a buddy from the optoelectronics department asked him to ask, not surprisingly, it should be the homework assigned by their teacher.

Three-day canteen small stove.

Now Han Yi doesn't say the specific value, which means that he didn't say it.

It's not over yet, the buddy who went out temporarily just sent him a message, and the teacher who assigned the homework is sitting on the stage now......

The time is almost up.

Just as the leaders of SUSTech were about to announce the end of today's seminar, a girl with white skin and beautiful skin and a pair of round-framed glasses on the bridge of her nose took the microphone handed over by everyone and said, "Mr. Han, can I ask you a question?"

Hundreds of pairs of eyes in the audience looked at it together.

When he saw who it was, he suddenly showed an expression of watching a good show.

This girl is Zhang Jian, the daughter of Zhang Mingfan, a doctoral supervisor in the Department of Mathematics of SUSTech, and her identity is not a student, but the youngest professor in the history of SUSTech.

Zhang Jian's resume is very brilliant, at the age of 18, he refused to be admitted to Mizuki University, but was admitted to Yan University with the top science score in Guangdong Province;

skipped a grade to finish at Yan University and went to Oxford University for further study;

Master's and doctor's degree in continuous study, three years to complete all courses, excellent in all subjects;

After that, he rejected offers from many large scientific research institutions in the UK, and resolutely returned to SUSTech to teach applied mathematics.

By the way, she's 24 years old.

When Zhang Jian spoke, several SUSTech leaders on the stage showed unnatural looks.

Under China's seniority system, which of them has not become a mother-in-law after many years of daughter-in-law?

Only Zhang Jian, who won the title of professor at a young age, didn't know how many people were jealous behind his back.

But the strength of the people is there, and it is useless to be unconvinced.

In addition, there is a doctoral supervisor Lao Tzu who is covered, and now she is the "first tyrant" of SUSTech; except for a few leaders, no one has a problem with her.

Han Yi, who was already planning to leave, smiled and said, "Is there anything this classmate wants to ask?"

"Huh-"

Han Yi's "lustful" smile immediately destroyed the aura of the "godfather of optics" in the minds of the students in the audience.

Just a few classmates asked questions, and I didn't see him so polite, but now their beautiful professor asked questions, and immediately became kind.

Sure enough, this is a year of looking at faces and talking.

Zhang Jian said: "I just read your answer carefully, if you follow the equations of the photon superposition method, I have reason to believe that real human-computer interaction will be realized, right?"

Han Yi was surprised in his heart, and secretly praised this girl for being really smart!

"Regarding human-computer interaction, there are many technical questions involved, and it is not convenient to answer them for the time being. ”

Zhang Jian nodded and said, "What I want to ask Mr. Han is, do you think the light needs to be pushed forward? ”

Han Yi said casually: "Light participates in the electromagnetic interaction between matter, and the static mass of photons is 0, which is not a material particle, and does not eat the set of resistance, so the propagation of light does not need thrust." ”

Zhang Jian followed up and asked, "Since there is no need for thrust, this means that the light is perpetually moving, in that case, why does the light disappear when the switch is turned off?"

Han Yi can see that this beautiful girl is deliberately finding fault.

After thinking about it for a while, he said: "It is well known that with each step of light in the medium, the change in its spectral line radiation is equal to the intensity of absorption, then ......"

Han Yi picked up the chalk as he spoke, and listed the formula in the only blank space in the lower left corner of the blackboard behind him, "According to Kirchhoff's law, the medium in the air not only absorbs light, but also emits radiant light;

The energy carried by the photons is absorbed by the medium, which heats the medium, and then this energy is released in the form of blackbody radiation.

So the light does not disappear, but interacts with matter and is absorbed;

Dilute below the detection limit of the instrument, and you will naturally be invisible. ”

"Bang Bang Bang-"

There was applause on and off the stage.

Zhang Jian nodded, and after the applause was a little smaller, he then asked: "After reading Mr. Han's equations on the photon superposition method just now, I have a little doubt in my heart......

The students at the scene, seeing that their beautiful professor was unrelenting, had a snickering expression on their faces.

A beautiful woman is still a scholar, and ordinary people are not blessed to bear it.

Can the technical cow in the stands carry it?

It's a good story to carry it.

Can't bear it, hehe......

Tomorrow, [the youngest professor of Jinshi University loses to the youngest professor of SUSTech] will become a front-page headliner.

Compared with the excitement of many students, the experts and scholars of SUSTech on the stage were a little crying and laughing.

Regardless of whether you can answer it or not, people are here to participate in academic seminars, not to accept your aggressive questioning.

Tang Lixian, the leader of SUSTech and the host of the scene in the background, said "It's just nonsense".

I was going to go to the stage to stop it, but so many experts and professors from fraternal colleges and universities are here, and now that they have gone up, isn't that smearing themselves?

Tang Lixian was so anxious that he was spinning in the background.

In the end, I had no choice but to contact Zhang Mingfan, the son of Zhang Thorn, first.

......

Zhang Jian ignored the excitement or complicated gaze at the scene, pointed to the blackboard behind Han Yi, and asked politely, "Can I go up?"

"Hmm. ”

Zhang Jian walked up to the wide podium from the middle aisle, put down the microphone, picked up the chalkboard on the main podium, and walked to the blackboard;

Ignoring the fire-breathing gaze of many experts and scholars, he erased a large piece of the equation written by Han Yi before, and said as he wrote: "Assuming that a stationary microscopic particle has a mass of m, there is a theoretical transition that can emit a photon with a frequency of ω;

So considering the recoil effect of photons, the frequency of photons that are actually emitted, and we replace them with φ, then the equation should be like this. ”

Zhang Jian wrote a long list of values, "Now let's make an order of magnitude estimate."

If this is a hydrogen atom, the transition, let's write the momentum a little bigger, the Lyman-alpha line of hydrogen, which is about 253.2 nm outside the vacuum;

From here we can see that the light emitted does not theoretically need a thrust, but the reaction force is an objective fact.

And it is precisely by the presence of reaction forces that laser cooling technology is possible.

Then the problem arises, if it is deduced according to the photon superposition method, the energy transfer between the two charged particles is carried out through the exchange of photons;

The forces they produce are bound to have a fundamental impact on human-computer interaction.

So I would like to ask you, how do you plan to overcome this?"

Han Yi gave a thumbs up in his heart.

The question raised by Zhang Jian can be said to hit the nail on the head!

He asked what he deliberately avoided and didn't want to talk about deeply.

At the same time, he also understood that the previous two questions were just bait, and the real purpose of the other party was this!

She was doomed to disappointment, though.

Looking at Zhang Jian's hopeful eyes, Han Yi said two words, "Guess!"

“......”