Why can people see without eyes?

As long as you want to

Record and comment on the classroom teaching of Science of Eyes

Teaching: Xue Hongxia

Comment: Kang Baomin

1. Introducing new lessons

Teacher: Students, people often say, "Eyes are the windows to the soul", and I will learn from your bright eyes.

health: I don't know. (Some students shake their heads)

Teacher: That is the strong desire to explore scientific knowledge. Eyes are very important and precious. So, what do you know about eyes? (Most students raise their hands)

S: You can see with your eyes.

health: the eyes are round.

health: when sand enters your eyes, you will cry.

health: when you look at things in strong light, your eyes will narrow into a crack.

Health: Myopia can only see the near objects clearly, but can't see the distant objects clearly.

teacher: you know a lot. what else do you want to know about eyes? (Most students raise their hands when their interest increases)

Student: Why can the eyes see objects?

health: how do the eyes see objects?

health: I wonder how the eyes are made up?

student: why do some students wear glasses?

health: I heard old people say that they wear reading glasses. What's the difference between them and the glasses worn by our classmates?

health: why can cats catch mice at night?

teacher: the students have asked so many questions, and I think there are mainly the following aspects: the structure and function of the eyes, and how do the eyes see objects? How is myopia formed? Types of eye diseases and knowledge about animals' eyes. So many problems can't be solved in one class. Today, we mainly solve two problems: First, how do the eyes see objects? Second, how is myopia formed? How to prevent it? This is the knowledge to be learned in Lesson 5. (writing on the blackboard)

2. Teaching new lessons

(1) Visual geneticist: Why can the eyes see objects? How does it see objects? To solve this problem, we must first understand the ... (teacher's finger eyes)

health: (qi) structure of eyes.

Teacher: Please touch your eyes. What parts do you think your eyes are made of? Which part is the most important? (Students touch their eyes with their hands)

Health: It consists of two parts: eyelids and eyeballs (the teacher corrected that eyelids are eyelids and eyeballs are spherical, also called eyeballs and eyelashes, which are the three parts we can see).

Health: The eyeball is the most important. Eyelids and eyelashes are used to protect the eyeball.

teacher: please look at each other's eyeballs in pairs to see what's in them. What can be seen directly? Combined with our own life experience, guess what else we can't see in the eyeball, and what role they may have. (Students in each group observe each other)

Teacher: Who would like to tell you what you have observed and thought?

health: there are bloodshot eyes.

health: there are three colors of eyeballs: the outermost is white, the middle is brown and the innermost is black.

health: I see some people have spots on their eyeballs.

health: I saw myself from my deskmate's eyes.

health: I see that the pupil becomes smaller when the deskmate's eyes are facing strong light, otherwise the pupil becomes larger.

health: because the eyes can see things, I guess there is an imaging structure in the eyeball.

health: the eyes can see both distant objects and nearby objects. I guess there may be a structure in the eyeball to see things clearly.

teacher: everyone observes carefully and is good at thinking. Are the students right? Let's watch a video called "The Structure of the Eyeball". When watching it, we should pay attention to remember the names of various parts of the eyeball in the video and what they do. (The teacher plays the video)

Teacher: After watching the video, please tell a classmate about the structure of the eyeball. (Slide: The Structure of Eyeball)

Health: The eyeball consists of pupil, lens, retina and optic nerve respectively. (The teacher writes on the blackboard one by one according to what the students say)

Teacher: What are the functions of each part?

Health: Pupils are the channels through which light enters the eyes.

students: the pupil can also be enlarged or narrowed to adjust the amount of light entering the eye.

students: the lens is a transparent lens, like a convex lens, which can be imaged.

health: the object is imaged on the retina.

Health: There are many photosensitive cells on the retina, which can sense the intensity and color of light. Only when objects are imaged on the retina through the lens can we see clearly.

Health: The optic nerve is connected with the brain and reports the signals on the retina to the brain.

teacher: we have figured out the eyeball structure. how do eyes see objects? Let's recall the principle of camera imaging last class and say how the camera takes pictures.

(Show the slide: Schematic Diagram of Camera Imaging)

Health: According to the principle of convex lens imaging, external objects form inverted and reduced images on the negative through the convex lens in the camera lens.

teacher: (slide: schematic diagram of visual causes) This is a schematic diagram of visual causes. What do your eyes look like?

health: camera. (Qi) < P > Teacher: Which part of the eye is equivalent to the lens of a camera? What does it do? Which part is equivalent to the negative, and what is its function?

health: the lens is equivalent to a convex lens, which is used for imaging, and the retina is equivalent to a negative film, which is used for light sensitivity.

Teacher: Since the process of seeing things by eyes is very similar to that of camera imaging, please combine the principle of camera imaging and the following three thinking questions to discuss in groups how the eyes see the whole process of objects.

projection: question:

1. can you see the objects around you without light?

2. what happens to the light emitted or reflected by external objects after passing through the lens? Where is the imaging?

3. Who "reported" the image of an object on the retina to the brain?

(The students discuss in groups of four, and the teacher participates in some group discussions, so the students are very involved and the discussion atmosphere is strong)

Teacher: Who would like to tell you the results of your group discussion? (The teacher shows the slide "Schematic Diagram of Eye Imaging", and the students rush to speak)

Health: Without light, you can't see objects. (Cover your eyes with your hands)

Health: The light emitted by external objects or reflected objects enters the eyes through the pupil, and is imaged on the retina through the lens. The nerves connected to the retina report these signals to the brain, and we see beautiful flowers.

Health: Some objects around us emit light by themselves, and some reflect the light of other objects. When the light emitted or reflected by them enters the eyes through the pupil and lens, images of these objects will be formed on the retina. The optic nerve connected to the retina immediately reports these light signals to the brain, and we see these objects.

Teacher: Everyone speaks very well. Please look at the model of eyeball (demonstrating that candles are imaged on the model of eyeball). Who can come on stage and tell the process of seeing objects with the eyes like a commentator?

Student: (Students explain the model) The light emitted by the candle enters the eyes through the pupil and lens, and is imaged on the retina. The optic nerve transmits the light signal imaged by the candle to the brain, and we see the candle.

teacher: the explanation is very good. To sum up, what are the two main reasons why eyes can see all kinds of objects around them?

students: there are imaging structures in the eyeball.

health: the eyes can be imaged.

health: there must be light.

(2) Formation and prevention of myopia Teacher: We have understood the causes of vision (blackboard writing), so what other questions do you want to explore?

health: why can the eyes see both distant objects and nearby objects?

Health: External objects form an inverted image on the retina. Why do we see an upright image?

health: how is myopia formed?

teacher: first of all, let's do an experiment that simulates eyes to see objects, and see if we can answer the questions raised by our classmates through this experiment.

teacher: this experiment is divided into three steps. (The teacher demonstrates and explains the experimental steps, and the students experiment in groups)

Step 1: Observe the experimental equipment, choose a lens with large convexity to do the experiment, light the candle and make the candle light pass through the convex lens to form a clear image on the paper screen. If there are no problems, let's start the group experiment now. (No problem, the students do the experiment in groups of four, and the teachers patrol and guide them)

Teacher: Now there are clear inverted images of candle flames on the paper screens of each group. Let's discuss and answer which parts of the eyes are the experimental equipment equivalent to in this experiment. Which part is equivalent to what the eye sees? (Students discuss)

Teacher: Please give a specific answer.

health: the structure of convex lens and paper screen imaging is like the structure of eyes. The convex lens is equivalent to the lens of the eye, the paper screen is equivalent to the retina, and the candle is equivalent to the object seen by the eye.

Step 2: Keep the object away from the convex lens (lens) (the teacher moves the candle outward by about 1 cm), and then observe what happens to the image on the paper screen (retina)? Note: In the experiment, the positions of "lens" and "retina" cannot be moved. (Students work in groups and report)

Student: The image on the "retina" is blurred.

Step 3: Replace the original convex lens with a convex lens with smaller convexity, and then do the experiment. What is the result? Note: The distance between the candle, the paper screen and the convex lens cannot be moved, but the convex lens is replaced. (Students experiment in groups and report the results)

Student: The image on the retina becomes clear again.

teacher: think about it, why? Please repeat this experiment and see what you find from it. (Students' experimental exploration and teachers' patrol guidance)

Student: The convexity of the convex lens has changed, and so has the image.

teacher: what does the convex lens mean in this simulation experiment?

health: lens.

teacher: whose change does the convexity change of convex lens represent?

students: the changes of lens convexity.

teacher: what do you understand through this experiment? What can you infer?

health: the lens convexity of human eyes can be changed.

Health: The lens convexity becomes larger, so people can see the near objects clearly, while the lens convexity becomes smaller, so people can see the distant objects clearly.

health: the lens convexity of myopia must be very large.

teacher: just now, several students guessed very well that the convexity of the lens of human eyes can be changed. Although it can't be changed like convexity. Although it can't change the lens like convex lens imaging, it can directly change the convexity of the lens and make people see the object clearly. Where's the secret?

Teacher: Let's do another experiment. Please take out your prepared balloons (inflated) and press them on both ends with your thumb and forefinger. This is the secret. It turns out that there are muscles at both ends of human lens, called ciliary muscles. Now I regard the balloon in my hand as the lens and my fingers as the ciliary muscle. What happens when you press the balloon hard?

health: when the finger presses the balloon, the convexity of the balloon becomes larger, that is, when the ciliary muscle contracts, the convexity of the lens becomes larger.

health: when the fingers relax, the convexity of the balloon becomes smaller, that is, when the ciliary muscle relaxes, the convexity of the lens becomes smaller. Health: When the lens convexity becomes larger, people can see the near objects clearly.

health: when the lens convexity becomes smaller, people can see the distant objects clearly.

teacher: these students basically described the process of people seeing things clearly.

teacher: now we need students to read books for a long time, that is, to look at nearby objects. (Students keep pressing the balloon with their hands for 2-3 minutes) < P > Teacher: Please describe the feeling of their fingers.

health: sour.

health: hard.

health: my fingers feel tired.

teacher: so when we look at nearby objects for a long time, will the crystal shape of our eyes get tired? If the lens is tired for a long time, will it return to its original state? We know that rubber bands cannot be restored to their original state without being relaxed for a long time after being stretched. Please think: How is myopia formed?

Health: If you look at near objects for a long time, the lens convexity is always relatively large, and the muscles pulling the lens are always in a state of tension. After a long time, the muscles will be tired and lose their ability to adjust. When you look at distant objects, the muscles will not relax, and the lens convexity will not decrease, and the imaging will be blurred, which will form myopia.

Health: A person always looks at the near objects, and the lens convexity is always relatively large, and the muscles at both ends are always in a state of contraction. When time goes its own way, he will be tired, unable to return to its original state, and the lens convexity will not become smaller. The distant image can't just form on the retina, and the object looks unclear, which makes him nearsighted.

teacher: did the students above answer correctly? Please watch the video "The Cause of Vision" and "The Formation of Myopia". (students watch the video)

Teacher: It seems that everyone's speculation is very close to the research of scientists, which shows that your reasoning ability is strengthening, so you should continue to work hard in the future.

teacher: myopia is a common phenomenon among primary and secondary school students. Statistics in 1996 show that the myopia rate of primary school students is 22.78%, that of middle school students is 55.22%, and that of high school students is 7.34%. And there is an upward trend. Myopia has brought a lot of inconvenience to our study and life. Do you know how to prevent myopia through today's study?

health: read and write correctly, and keep the distance between eyes and books about one foot.

health: don't read or write in direct strong sunlight or very dark places.

health: don't read while lying down, walking or riding.

health: do eye exercises seriously.

health: read for about an hour, take a break for a few minutes, look far away for a while, and you'd better look at the green plants.

teacher: I hope you will keep your word, protect your eyes and let them serve us better.

III. Consolidate knowledge

Teacher: (Reading on the blackboard) Today, students explored the structure of eyeball, the causes of vision and the formation and prevention of myopia by themselves through observation, speculation, experiment and discussion. We not only mastered some science about eyes, but also understood the importance of protecting eyes. More importantly, we learned to speculate based on the facts and the existing knowledge. I hope you can apply this learning method to your future learning activities.

In this class, everyone actively used their brains and spoke enthusiastically, and raised many questions. Let's ask and answer our own questions through student-student interaction.

Health Q: Why do cats' eyes "change three times a day" Health Q: In order to help mice, their pupils become bigger at night and their eyes can see clearly.

health question: why do you cry when your eyes accidentally enter the sand?

Health Answer: Eyes can secrete tears, wash eyeballs and play a protective role.

student q: I wonder if there are any other types of myopia?

A: Myopia can be divided into true myopia and false myopia.

Dr. Q: According to the eye imaging model, the object is imaged upside down on the retina, but why do we see it upright?

Q: Are the eyes of insects the same as those of people?

health question: why does the eagle's eyes see farther than people?

Q: Why do the frog's eyes bulge outward? Student: Why are rabbit's eyes red? Student: Why are tears salty?

teacher: the students are really amazing. Through your own study, many problems have been solved, which shows that you love science and can learn, and hope to continue to carry it forward in your future study and life. There are still some problems that didn't come today.