20 years of teaching

Chapter 217 Popular Science Education
"Ms. Lin, can you beat the gongs and drums for us to hear?" Li Tuanjie, who was sitting behind, shouted.

"Okay! Listen to Teacher Li." Lin Feifan picked up two sticks and beat the gong and drum.

Dongbeng, Dongbeng, Dongbeng, Dongbeng, Dongbeng...

So everyone in the classroom burst out laughing...

Only Li Tuanjie was stunned. When he saw the gongs and drums on the podium, he wanted to make a joke, but Lin Feifan actually beat the gongs and drums...

After finishing playing a piece of gong and drum music, Lin Feifan stretched out his hand and pressed it down like a palm. All the students in the classroom immediately quieted down, and those who hadn't finished laughing tried their best to hold back.

Only Chief Yang was still coughing. In fact, Chief Yang couldn’t stop laughing, but now that one person is still laughing, that’s a breach of classroom discipline, so he turned his laughter into a coughing sound to cover up that he couldn’t help but laugh. ...

Lin Feifei took the opportunity to add that all the sounds produced by musical instruments are musical tones. From a physical point of view, the vibration of musical tones is regular.

There are natural musical sounds in nature, such as the chirping of birds, the sound of running water in a stream, the spring breeze blowing the grass, the drizzle moistening the green leaves, etc.

The sound of beating gongs and drums is noise, and the vibration of noise is irregular and chaotic.

And gongs and drums are also a kind of musical instrument. If they are beaten randomly, they will be harsh and unpleasant, but if they are played with a beautiful rhythm, they can also form beautiful music.

Finally, Lin Feifei added some knowledge about ultrasound and infrasound that was not in textbooks.

Sounds above 20000 Hz are called ultrasound, and sounds below 20 Hz are called infrasound.

The frequency of human perception of sound has a certain range, and most people can hear sounds from 20 Hz to 20000 Hz.

Ultrasonic waves and infrasound waves are not within the hearing range of the human ear, so people cannot hear them.

When a fly flies, it vibrates its wings 147-200 times per second. The frequency (f) is the frequency of sound source vibrations per second. within range.

When a butterfly is flying, it vibrates its wings 5-6 times per second, that is, the frequency is 5Hz-6Hz, which is not within the hearing range of the human ear.

So we can detect flies in flight by hearing, but not butterflies in flight.

Infrasound waves are produced when earthquakes, volcanic eruptions, typhoons, tsunamis, nuclear explosions, and missile launches occur.

On the eve of an earthquake, the phenomenon of "chicken flying and dog jumping" often occurs, because the infrasound waves generated can be heard by many animals.

Therefore, if you find that many animals have abnormal reactions, such as chickens clucking in panic, dogs jumping around and shouting, snakes crawling out of their holes, mice all over the street, earthworms, frogs, etc. , you should be vigilant, it is very likely that an earthquake is about to occur.

It is said that after the tsunami, the dead animals were rarely found because they heard the infrasound waves in advance and fled.

They also want to tell people, but unfortunately people can't understand their language, so they have to tell humans with actions, but humans still ignore them and call them crazy...

"Puff—cough cough—cough—" Section Chief Yang in the back row couldn't help laughing again, and pretended to cough to cover up...

Lin Feifei paused for a moment, and continued talking about the mountain after Chief Yang's violent cough subsided.

The hearing range of most animals is wider than that of humans. For example, dogs have a hearing range of 15 Hz to 50000 Hz, so dogs are very sensitive. If you have a dog at home, thieves are afraid to come to your door.

Dolphins can hear sounds up to 150000 Hz. They use ultrasound to communicate, and bats also emit ultrasound, using the principle of echolocation to prey.

Elephants, on the contrary, can emit infrasound waves, and they use infrasound waves to keep in touch with each other.

Ultrasound has good directionality, strong reflection ability, and is easy to obtain concentrated sound energy. The propagation distance in water is farther than in air. It is widely used and can be used for distance measurement, speed measurement, cleaning, welding, gravel, sterilization and disinfection, etc.

There are also many applications of ultrasound in medicine, military, industry, and agriculture. For example, sonar is installed on submarines to judge the orientation of surface ships, and fishermen use sonar to find fish schools.

The most common application of ultrasound is B-ultrasound. The B-ultrasound diagnostic instrument emits ultrasonic waves. After it is injected into the human body, the reflected waves formed in the tissues and organs of the body return to the ultrasonic diagnostic instrument.

Then, through the high-energy electronic computer in the ultrasonic diagnostic instrument, the energy conversion of sound energy and light energy is performed to form an image, which is used in ultrasonic diagnosis.

Doctors use B-ultrasound to check whether there are lesions in the human heart, liver, gallbladder, spleen and other organs, as well as to check the development of the fetus.

Advanced scientific methods are sometimes used by criminals. For example, a small number of doctors with bad conscience use ultrasonic diagnostic equipment to identify the sex of fetuses and earn black-hearted money...

In the state of natural fertility, the ratio of male to female is close to one to one, but now the ratio of male to female is seriously out of balance...

Technology is a double-edged sword!
The dual effects of patriarchal outdated ideas and advanced technology will lead to countless bachelors in society after many years.

Male students must study hard, otherwise, when they grow up, they may not be able to find a wife and become bachelors.

Of course, girls have to study harder, strive to be better than boys, use their own hard work to achieve achievements, and change the perception of those who have prejudice against girls...

Without women, how can we pass on the family line?Genetic material, from both parents...

The extra topic in just a few words made both boys and girls feel excited.

Uh-huh!Be sure to study hard and work hard!
……

……

……

Unknowingly, it changed from music class to physics class again. Li Tuanjie listened with great interest. He was glad that he took the initiative to attend the class and received a perfect science education today.

Lin Feifei finally said: "This is the end of this new lesson. After class, please preview the content that has not been finished in this section. Today's class assignment is the first, second and third questions on page 22 of the textbook. Next I will ask questions about the content of this lesson, please recite all the knowledge points of this lesson after class."

"Dangdangdang——" The bell rang for the end of get out of class.

"Students, get out of class!" Lin Feifei smiled, how could the timing be so accurate?

All the students stood up and bowed to Teacher Lin in unison, "Teacher, thank you for your hard work. Goodbye, teacher!"

Wang Boda stood there in a daze. He looked around the walls to see if there were any clocks on the walls. He clearly saw that Lin Feifan was not wearing a watch. How could the time be so accurate?

get out of class is over as soon as the lecture is over, a second is not bad!

It is a common problem of most young teachers that they cannot effectively arrange a class of 45 minutes.

Yin Qinsong next to him said, "Lin Feifan doesn't look like he was assigned just after graduation, but more like an experienced teacher. Director Wang, you teach well!"

Wang Baida was flattered, and said with a smile: "The main reason is that Lin Feifan is very obedient, he will do what I say."

Liu Fuliang's face was livid, and he was so angry that he wanted to find Lin Feifan's shortcomings by opening the door to listen to the class, but he didn't find any shortcomings, but the advantages emerged one after another. I won a prize.

Several people commented on this class in the corridor, and they all talked about the advantages. Even Ma Jingzhou, who was one-hearted with Liu Fuliang, said that he had never heard such a wonderful class in all these years. Very frequently, the classroom atmosphere is very active, giving full play to the subjective initiative of the students...

Chief Yang was the director of the teaching and research section of the Education Bureau before he was promoted to the chief of education. In order to show his incisive insights into classroom teaching, he only commented on the aspect of teaching procedures.

He said that Lin Feifei's teaching ideas are clear, the classroom structure is rigorous, and the teaching density is reasonable. The whole class is aimed at all students, but it also reflects individual differences. He teaches students in accordance with their aptitude, which comprehensively improves the quality of students...

Chief Yang was eloquent, dancing, and spitting. He especially pointed out that the amount of knowledge imparted and the ability to be trained in this class were moderate, highlighting the key points, grasping the difficulties, creating opportunities for students, and allowing them to actively participate in the class. , take the initiative to seek knowledge, figure out the process of knowledge formation, and the experimental conclusions are drawn by the students themselves. This is a very successful public class.

……

(End of this chapter)