Xiao Fei talked about physics again, physics is not my strong point, so I had to listen to it on the sidelines. "Have you ever heard www.biquge.info of such an experiment?" Our ancestors were very clever and had very accurate meteorological observations in the Han Dynasty, which was the famous experiment of carving fish to measure rain. ”

"Brother Xiaofei, we haven't heard of it. Tell us about it. A bunch of children couldn't wait. These children are naturally lonely and ignorant of the world, so it is understandable that they don't know, but I am not interested in physics, and I usually don't pay much attention to them, so I also shook my head with them. Xiao Fei said patiently: "This is a strange physical experiment that is done in this way, and the instrument it uses is a fish carved from jade. This fish is oval-shaped, hollow, and has both a mustache and a tail. The aim is to predict the weather with the roar of the fish. There is a detailed record in the "Xijing Miscellaneous Records", and interested students can go back and check it. It is about the Kunming pond carved jade for the fish, every thunderstorm often roars, and the tail of the beard moves. The prayer for rain in the Han Dynasty is often tested. May I ask you, dear students, why is this? Do you have any ideas, please speak out boldly. ”

After a moment of silence, a chubby child stepped forward, he shook his head and said, "I think, it must be a magical stone, the jade was left by the fairy grandfather." Another child suddenly realized: "It's not left by the gods, it's the stone left by Nuwa Niangniang when she mends the sky, that's why it's so effective." Xiao Fei smiled slightly: "Your imagination is quite rich." In fact, it is due to the clever use of the resonance effect in this experiment, not the reason for the stone fish. But those who don't know the principle have admiration for the stone fish and worship it. We know that when there is a storm, strong winds passing over the sea surface will produce infrasound waves, infrasound waves and storm roaring sound waves together in all directions, sound waves are easily swallowed, only very low frequency infrasound waves in the propagation process of energy loss, travel distance, many times faster than the speed of wind and waves, it can become the alarm of the coming storm. But infrasound cannot be distinguished by the human ear. The stone fish is such a storm alarm: it opens its mouth, its stomach is empty, and when the infrasound waves constantly exert periodic external force on it, the stone fish is forced to vibrate. If the dynamic frequency of the sound wave is a multiple of the natural frequency of the stone fish, the stone fish produces a nonlinear resonance and emits sound waves. Among them, the high-frequency part is audible sound. At this time, the tail of the stonefish should move, and its acoustic effect is manifested as a loud roar. In fact, in ancient times, there were countless examples of using the resonance effect to predict weather, earthquakes, and military rebellion. During the time of Emperor Wu of the Han Dynasty, the bell in front of Weiyang Palace rang for no reason, and it did not stop for three days and three nights. The edict asks Taishi, and when he waits for the edict Wang Shuo, Shuo Yan is afraid that he will have military spirit. It can be seen that the fish rain measurement experiment has a solid theoretical foundation, and these theories are summarized in continuous observation and analysis. There was such a wonderful experiment in the Han Dynasty in our country, which is something that we are proud of as the descendants of Yan and Huang. ”

There was a cheer below, and I was also watching with interest on the side, I really learned mathematics, physics and chemistry, and I was not afraid to go off the beaten track, and now it should be changed to ancient and modern. I have a deep understanding, who called me a science student? Now I have to obediently listen to Xiao Fei's smug speech.

He also showed you several interesting physics experiments, such as copper mirror transparency. This kind of mirror is called "translucent mirror" and began in the Western Han Dynasty. Together with chimes and fish washes, it is known as the Three Treasures of Ancient Chinese Bronze. When Xiao Fei displayed it in the hall, this magical mirror can not only reflect people's faces, but also when the beam of light hits the mirror, the inscription pattern cast on the back of the mirror will also "see" through the mirror and appear on the wall of the house, which is clear. "So how can the bronze mirror transmit light?"

Seeing that everyone was stunned, Xiao Fei lost no time in asking. Everyone looked at each other blankly, Xiao Fei smiled slightly, and said proudly: "This is because after the translucent mirror is cast, the mirror surface will have small fluctuations corresponding to the inscription on the back of the mirror that are not easy to detect with the naked eye. When the mirror is ground to a certain extent, these factors work together to make the mirror produce a curvature corresponding to the inscription on the back of the mirror. When the beam shines on the mirror, the slight fluctuations of the mirror are amplified by the optical path, and the light transmission effect is revealed. I see, everyone nodded thoughtfully.

Xiao Fei took out a beautiful cup in the shape of an ancient butterfly, which was beautiful, but it looked similar to other cups and was not strange. Xiao Fei smiled slightly, "Now that we pour water into the cup, it's very different, let's see the magic of the cup in the picture." ”

Everyone's eyes widened, and sure enough, the cup was filled with water, and there was a lot of mystery in it, only to see two smart and lovely butterflies dancing in the middle of the water cup, lifelike. Xiao Fei asked: "Why is this? Everyone needs to know what it is, and why it is." ”

But everyone still looked at each other, I don't know why. Xiao Fei held the cup and explained in detail: "Because a convex lens is embedded in the center of the bottom of the cup, and the colored butterflies are loaded with a hairspring in the foot of the cup, as long as the cup is slightly disturbed, the colored butterflies can dance." When there is no wine in the glass, the butterfly is outside the focal point of the convex lens, causing a real image on the same side as the human eye, and the human eye is blurred. After pouring the wine into the glass, this transparent wine becomes a concave lens, and the convex lens and the concave lens are combined to form a compound lens. The focal length of the compound lens is larger than that of the convex lens, and the butterfly falls within the focal length of the compound lens, resulting in a magnified virtual image, which is located at the photopic distance. The compound mirror acts as a magnifying glass, allowing the human eye to clearly see the magnified butterfly. Because the cup is always disturbed in the hand, the butterfly will dance. ”

So that's the case, so everyone suddenly realized and applauded. I really don't know where Xiaofei acquired these precious antiques, this technology has long been lost, this butterfly cup cup is really priceless, if it can be brought to modern society, it is guaranteed that another multimillionaire will be born, I can't help but look at it with admiration.

Xiao Fei unhurriedly took out the flask, and the pieces of paper, etc., and said while dancing with long sleeves: "Now, we are going to use egg white, alum powder and evenly coated paper to make Cho Zi, and put it on the flame to make sencha, everyone think about it, what is the result of this experiment? Is the water boiling and the paper not combusting, or is the fire directly burning the paper? Let's wait and see." ”

This paper burns when it is on fire, but the water is boiling and the paper is always unharmed, which is amazing. Seeing that everyone looked puzzled, Xiao Fei took the trouble to explain patiently: "The flame temperature is about 600C, and the ignition point of the paper is 183C. But with paper Choshi sencha, the situation is different. When the furnace fire burns, the water inside Choshi continuously absorbs heat and cools the paper. The boiling point of water is 100C. The water will turn into vapor at this temperature, and the excess will be tropic, so the boiling water temperature will not exceed 100C, which is lower than the ignition point of the paper, and as long as the water in Choshi does not dry out, the paper will not burn. Everyone nodded, showing the same expressions.

Just after demonstrating this interesting experiment, after everyone's eyes were opened, he hurriedly came up with a beautiful water spray fish wash. This ancient toy began in the Han Dynasty, and most of them resemble washbasins, with fish carved on the bottom of the basin and two ears on the rim of the basin. Xiao Fei gently rubbed the two ears, the basin sprayed out a stream of more than half a meter high beautiful water column, in the mottled eyes reflected from the window, the colorful rainbow loomed, everyone saw it is really breathtaking, but this fish wash in modern society has many antique shops, but it has not been lost, and it is not so rare, but I don't know why this is so, and now I can finally find out.

Xiao Fei Zhenzhen said: "The principle of water spraying is actually the four-line vibration wave generated by vibration that causes the agitation of water, and the vibration process is similar to the air vibration of a round clock. In order to make the fish wash spray water, the palm of the hand should be rubbed against the ears of the fish wash, as an excitation source for the vibration of the wash. The position of the palm can be regarded as the position of the vibration wave node, so that due to the symmetry of washing, its vibration can only produce an even number of knots, and the vibration of the beating wave makes the water in the washing produce corresponding harmonic vibration, so that in the belly of the vibration wave of washing, the vibration of water is the strongest, and at the washing wave node, the water does not vibrate. "The mystery that I have been puzzled about is finally solved under Xiao Fei's in-depth explanation.

"After listening to me talk so much, I guess everyone is tired of listening, so let's do a little experiment and enliven the classroom atmosphere. This experiment is very simple, and now everyone works in pairs and does the experiment together. ”

Xiao Fei and I each took a bamboo tube and stood at both ends of the room to demonstrate, and asked the children to imitate: "Let's take two bamboo tubes now, empty both ends, and seal one side with leather paper." Two cylinders of paper face each other, take a few zhang long thin line through it, two people each hold the bamboo tube to stand far away, one mouth to the bamboo tube, one ear to listen to the bamboo tube, although a few zhang apart, but the speaker speaks at will, the person who listens to the opposite side knows, and the others do not know, everyone try it, see if it is so?"

When everyone heard that it was so magical, they immediately became interested, and while experimenting with the gourd painting scoop, they happily communicated.

It is really entertaining, not only to spread knowledge, but also to drive the enthusiasm of children, and to cultivate their hands-on ability, it is undeniable that Xiaofei is really a rare excellent teacher of the Great Song Dynasty. Just imagine, if my physics teacher at that time had such a level, my physics grades would not have dragged me down for so long, causing me to not perform well in the college entrance examination, and I will not be able to return to my home today, and I will be stranded in ancient times for a long time, and I don't know how long the deadline is? I don't know if it is a lifetime time? Hey, it makes people shudder to think about it, or don't think about it again, otherwise I will be discouraged and depressed, and then it will be all over. Fortunately, you are not an island at any time, no, isn't there still Xiaofei? What are you afraid of, don't think nonsense, those who go crazy are definitely not crazy about doing things, they are 100% crazy in thinking about things. So as soon as man thinks, God laughs. It's better to think about this thing in moderation, otherwise it will be miserable to think about it and become Nietzsche, and I quickly diverted my attention back.

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