Li Ang put the chopsticks in the empty glass, and then walked down, walking step by step in front of many emperors and grandchildren, to ensure that all the emperors and grandchildren could see the straight chopsticks and empty glasses, and from time to time he also took out the straight chopsticks to let everyone see more clearly.

The expressions of the eight old guys sitting in the town looked tall and disdainful, of course the chopsticks are straight, can they still be bent, this is simply a waste of time and life.

After making sure that everyone could see that the chopsticks were straight, Ang Lee returned to the podium, poured most of the water into the glass, and then put the chopsticks into the glass again, and at this time, it was clear through the glass that the chopsticks were bent, and the bend was quite obvious.

"Let's take a look again, is this chopstick still straight?"

Li An said, and walked down the podium again, letting everyone watch the appearance of chopsticks soaked in water.

Among them, ordinary people in later generations often see this phenomenon, and they can find it when they brush the dishes, but the people who come to listen to the lectures are the delicate emperors and grandchildren, and they have no chance to brush the dishes, of course, in addition to brushing the dishes, they also have various other opportunities to see this phenomenon, such as by the pool, so most of the emperors and grandsons should know that the straight rod will bend after being put into the water, but why this phenomenon occurs, they are not very clear.

"Bent, chopsticks bent."

I don't know who said it.

Li An smiled at the corner of his mouth and said, "That's right, the chopsticks I saw are also curved, but are these chopsticks really curved?" Take it out and take a look. ”

After taking out the chopsticks, everyone could see very clearly, the chopsticks were still straight, not bent at all, but after being put into the water again, they bent again, Ang Lee experimented many times in a row, and the results were the same, every time the chopsticks were put into the water and bent, and after taking them out, they became straight.

Seeing the different expressions of the emperors and grandsons, Li An suddenly frowned and said: "These chopsticks are straight on the outside, you can all see it, but after the chopsticks are in the water, whether they are straight or curved, who will say." ”

"Bent, bent, the chopsticks are bent when they get into the water, and they are straight again when they are taken out."

"Chopsticks are straight, they have always been straight, how can it be curved."

"Hmph, it's obviously bent, but the chopsticks become bent when they get into the water."

"Chopsticks are hard, water is soft, and chopsticks can't become soft when they get into the water, let alone bend."

"You said that chopsticks can't be bent in the water, so why are we bending?"

Good guy, Li An didn't pay attention, these emperors and grandsons actually quarreled, ordinary people are very angry, not to mention these nobles.

Of course, the quarreling emperors and grandsons only account for about one-third of the total number, and some are watching the excitement, some are frowning and thinking about the mystery, and there are a few distracted guys who don't know what they are thinking.

At such a young age, it is unlikely that they will think about girls, and they are most likely to think about what good things to eat after school, or have other things on their minds.

The study venue suddenly fell into a quarrel, and the eight old guys sitting in the town should have come out to stop this behavior, but because they were also thinking for a while, they actually forgot their most important task.

"Chopsticks are hard and won't bend when you put them in water, but why do they look bent?"

A younger old fellow said with a frown in his own words.

When the old guy next to him heard this, he also frowned secretly, and he really couldn't figure out what was going on.

"Silence, silence, everyone listen to me."

Li An personally shouted, telling the emperors and grandsons not to continue arguing.

Maybe it's because the content of Ang Lee's class is relatively novel, or maybe these bear children also want to know what the situation is, so when Ang Lee asks for silence, these guys who are arguing all shut up, and look at Ang Lee very curiously, wanting to know the answer to the bending of the chopsticks in the water.

Seeing that all the emperors and grandsons had stopped arguing, Li An smiled with great satisfaction and said: "Someone just said that chopsticks are hard, water is soft, and chopsticks are naturally straight when put into water, of course they will not be bent, there is no doubt about this, otherwise, why is it still straight after taking it out?" Ha ha! I know, and some people must be asking, why do chopsticks look like they are curved when they enter the water, when they are always straight? Why is that? Does anyone know the answer? ”

After speaking, he looked at the emperors and grandsons, waiting for the answers of these guys.

"Sir, I know."

A teenage emperor stood up very confidently, his expression quite proud.

Suddenly, everyone's eyes were on this imperial grandson, including the eight old guys sitting in town.

Li An has seen this imperial grandson, it is the eldest son of the sixteenth son of the emperor, Li Hao, who looks like a naughty boy, about thirteen or fourteen years old.

"Very good, Li Hao, tell me, why is this? Why do straight chopsticks look bent when they get into the water? ”

Li Wei looked at the blackboard in the distance and said loudly: "This is because of the reflection and refraction of light. ”

After speaking, he looked at everyone proudly.

I have to say that this kid is really smart enough, the content of Ang Lee's class is the refraction and reflection of light, so the reason why chopsticks bend in the water is naturally the refraction and reflection of light.

Li An nodded with great satisfaction, and asked with a smile: "Li Hao, what you said is not accurate enough, the refraction and reflection of light are two phenomena, do you think the chopsticks are bent, is it the reflection of light, or the refraction of light?" ”

After speaking, he looked at Li Wei very expectantly.

"This is a reflection, or a refraction."

Li Hao naturally didn't understand this question, and opened his mouth in a rogue tone.

The rest of the people listened to Li Hao's words, and they all focused their attention on reflection and refraction.

Li An didn't want to continue to sell Guanzi, so he smiled and said: "The phenomenon that chopsticks bend in water is the refraction of light, which is one of the main contents of our lesson, so, what is the refraction of light?" ”

After a slight pause, Ang Lee continued to explain: "The refraction of light is a phenomenon in which the direction of propagation changes when light is shot from one substance into another, such as the bending of chopsticks. ”

After speaking, Ang Lee spent a figure on the blackboard, a chopstick inserted diagonally into the water, and an image of the chopsticks bent in the water, as well as some refractive lines.

"Before looking at this figure, I want to tell you that the reason why human eyes can see things is because the light on the object enters the human eye, not that the human eye will glow, if you put a person into a secret room without light, then he can't see anything, everything around him can't see, and when there is no moonlight and starlight at night, it is difficult for us to see things, and only when there is light around us, we can see things, which is enough to show that the premise of people seeing things, It's the light that glows or the light reflected on the thing that enters the human eye, so that we can see things, you think about it, is that the truth? ”

Li An said.

This theory is a little too trendy, not only the many emperors and grandsons who came to listen to the lecture felt incomprehensible, but the eight old guys who came to suppress the formation also felt incredible, thinking that Li Ang was talking nonsense.

"Sir, we can see the words on the books now, and it is the light from the books that enters our eyes, why is there no light in the books at night?"

An imperial grandson asked.

Li An smiled and said: "This question is very simple, during the day, there is light on the books, but this light is not the books themselves, but the sunlight is reflected to the books step by step, the sunlight shines on the ground, the ground will reflect part of the light to the walls and pillars outside, and the light on the pillars will reflect to our room, the tables, chairs and beams in the house will continue to reflect the light, and naturally the light will be reflected on the books, so that there will be light on the books, and it can enter our eyes, so that." We can also see the content of the book, but there is no sun at night, and naturally it is dark everywhere. ”

The emperors frowned and thought about it, feeling that what Li An said seemed to have some truth, and he was completely able to rationalize his thinking, and even the eight old guys in charge also had a certain recognition of Li An's words.

Li An struck while the iron was hot and continued to speak: "At night, we can light candles, or turn on the lights, so that there will be a light source, but because the light of the candlelight is too small, the reflected light is also very weak, so it is not enough to illuminate the whole room, so when we use candlelight to read at night, we will feel that the light is very dim, far less convenient than reading during the day." ”

After saying this, Ang Lee began to explain the optical path diagram on the blackboard, the optical path diagram of light refraction in water and air, and explained it very carefully.

For example, the law of refraction of light, refracted rays, incident rays and normals are in the same plane, refracted rays and incident rays are separated on both sides of the normal, when light obliquely enters other media from air, the angle of refraction is less than the angle of incidence, when rays from other media obliquely into the air, the angle of refraction is greater than the angle of incidence, the angle of refraction increases with the increase of the angle of incidence, when the ray rays are perpendicular to the surface of the medium, the direction of propagation does not change, then the angle of incidence and the angle of refraction are zero.

Because it is the first time to contact the knowledge of optics, although Li Ang explained it very carefully, these emperors and grandsons could not fully understand, and it is estimated that they will have to explain it several times to deepen their impression.

Of course, there are also a few emperors and grandsons with relatively high qualifications, and it is really commendable that at this time when Li Ang is in class for the first time, he can understand a rough idea.

And the eight old guys who were full of poetry and etiquette listened to it in the clouds, and felt that their brains hurt, and then they simply stopped listening.

"Guys, who can give an example of the refraction of light in life."

Ang Lee asked.

"I know that when catching fish, the fishing fork should be a little lower, not directly aimed at the fish, otherwise the fish will definitely not be forked."

An imperial grandson immediately said, it seems that he must have gone to spearfish, otherwise, it would be impossible to even know this little secret of spearfish.

Ang Lee was very happy to agree: "Very good, what I said is very correct, the spearfish can't be aimed at the fish, it should be slightly lower, who else can give an example." ”

"The bamboo pole that holds the boat looks bent."

An imperial grandson replied cautiously.

Li An smiled: "This is true, but this is the same thing as putting chopsticks in water, and who can give a better example." ”

"A telescope can see a long distance very clearly, and this is also the refraction of light!"

An imperial grandson said.

Li An nodded very happily and said happily: "That's right, come, I'll draw a map of the light path of the telescope, you can take a good look." ”

After drawing the light path diagram, I also spent some time to explain in detail, so that these emperors and grandsons who listened to the lecture could understand and understand.

In fact, the essence of the telescope is magnification, the distant scenery is refracted inward when entering the convex lens of the telescope, and the reverse extension line of the refraction is much larger than the original scene, and the scenery seen in the eyes has become larger, and the more intuitive feeling is that the scenery has become closer to itself, which is the principle of the telescope, which is very magical.

At this moment, telescopes have been popularized in the aristocratic class, especially the royal class, almost one person, and these royal grandchildren are naughty children, naturally they often play with telescopes, and they naturally have a better understanding of the characteristics of telescopes.

"Who else could give a better example of refraction."

Ang Lee continued to ask.

"Rainbow, there will be a rainbow after the rain, is it also refracted from it."

A very young guy said guessingly.

Li An nodded with satisfaction and said: "Very good, the rainbow we can often see is also produced after the refraction of light, but there is something to say about the rainbow, do you know what color the sunlight is?" ”

"The sun is red."

"No, it should be white."

"The sun should be golden."

"You say that sunlight has no color."

When it came to the color of the sun, the little ones argued again, and this was the atmosphere that Ang Lee liked very much.

"Haha! Sunlight is colorful, red, orange, yellow, green, blue, purple, all kinds of colors. ”

Ang Lee opened his mouth to give the answer.

"Colored, how can it be colored."

The emperors and grandchildren refused to believe it.

"How can the sunlight be colorful, Li Shilang is trying to teach the emperors and grandchildren badly!"

"Daylight colorless, colored? It's just nonsense. ”

The eight old guys in charge looked a little disdainful, but they were also somewhat curious in their hearts, wanting to see how Ang Lee would explain.