the world of silence

Imagine what a quiet world would be like.

In our colorful world, sound plays an important role. What would the world be like without sound? Let's imagine what kind of world it would be. Is it interesting? Cold? Quiet? or ...

Man is the master of the world. First of all, what effect will sound have on human beings? Then let's talk about the influence of sound on human beings first! What will happen to human beings if there is no sound? If there is no sound, people can't make a sound when they speak, just like people who lose their voices speak in sign language. Why do people need ears? There is no sound to listen to. Is it for decoration? How can there be such beautiful music now? If there is no sound, what is the point of the whole world dying in a dead universe? If there is no sound, how can students study and read at school? How can there be music, English, information ... courses? How will you express what you want to express? Do you rely on sign language? I really can't imagine what teaching would be like at that time.

Pangu, the ancestor of China, created human beings because he thought that the world was too quiet and lifeless. Now, if there was no sound, there would be no laughter. Then why are there humans? What's the point of having humans? We are not Beethoven, nor do we have Beethoven's skills. Even if we can't hear, we can bite a stick with our teeth and feel the sound according to the vibrating skull. But if there is no sound, not even sound waves, even Beethoven can't feel the sound, let alone play the piano. If there is no sound, how can there be a telephone now? If relatives are far away, how will they talk? Can you sign language after such a long distance? If … if … if too much, I think these ifs are impossible. In short, human beings need sound.

It's hard to imagine how human beings would survive without sound! Of course, this is not just human beings; Animals also need sound, and even animals can't live without sound; For example! Bats can be said to be a special kind of animals. Although it has a pair of eyes, it can always see if it can't hear, but do you know it is called "blind" in the animal kingdom? Its eyes are not worthy of the name, because it relies on its ears. Listen to ultrasonic waves with your ears to identify positions and avoid obstacles. If there is no sound, the bat can't hear the sound, can't catch the food and can't fly, then does it still have a chance to survive? Of course, bats are not the only animals, and other animals cannot do without sound. Here is an example to emphasize that "the earth cannot live without sound".

Without sound, people seem to live in a vacuum, quiet and silent. There is no wind, no rain, no reading, but more birds, songs and laughter. Therefore, the universe in which human beings live now has no color and no sound.

2.5. Introduce the camera

Generally speaking, the working principle of a camera is to use the optical imaging principle to image an object on a photosensitive material through a photographic lens. The following will briefly introduce the principle of photographic optical imaging: human understanding of the nature of light, the propagation of light and the principle of lens imaging.

Human understanding of the nature of light has gone through a long and tortuous process. In the whole18th century, the particle flow theory of light is still dominant in optics. It is generally believed that light is composed of tiny particles, which are emitted from point light sources and radiate in all directions in a straight line. /kloc-At the beginning of the 9th century, the works of Yang and Fresnel gradually developed into today's wave optical system. Now, the understanding of the essence of light is that light, like physical objects, is a kind of substance, which has both the properties of wave and particle (quantum), but as a whole, it is neither wave nor particle, nor a mixture of the two.

In essence, light is no different from ordinary radio waves. Like electromagnetic waves, light is a shear wave, that is, the vibration direction of the wave is perpendicular to the propagation direction. Luminous body is the emission source of electromagnetic wave, and the electromagnetic wave emitted by luminous body propagates to the surrounding space, similar to the wave generated by water wave fluctuation. The distance between two points with maximum or minimum intensity is called wavelength, which is denoted by λ. The time required to propagate a wavelength is called a period, which is represented by t, and the period is the time required for a particle to complete a vibration. The number of vibrations in 1 sec is called frequency, which is expressed by nu. The distance that vibration travels through 1s is called velocity, which is represented by "v". There are the following relationships among wavelength, frequency, period and speed:

v=λ/T，ν= 1/T，v=λν

It can be seen that the wavelength of light is inversely proportional to the frequency. In fact, light waves only account for a small part of the entire electromagnetic wave band. The electromagnetic wave with the wavelength of 400 ~ 700 nm can be felt by human eyes, which is called visible light. Beyond this range, the human eye will not feel it. Different wavelengths of visible light produce different color sensations in our eyes. According to the wavelength from long to short, the color of light is red, orange, yellow, green, cyan, blue and purple. The propagation speed of electromagnetic waves with different wavelengths in vacuum is exactly the same, and the value is c = 300000 km/s.

Here are some basic laws of geometric optics-the law of light propagation:

(1) The law of linear propagation of light in a uniform medium, that is, light travels along a straight line, that is, light is a straight line in a uniform medium. The phenomenon of linear propagation of light can be seen anytime and anywhere in daily life, such as objects turning into shadows after being irradiated by light, pinhole imaging and so on. The linear propagation of light leads to the concept of light.

(2) The Law of Independent Propagation of Light The propagation of light is independent. When different rays pass through a certain point in the medium from different directions, they do not affect each other. When two rays converge at a certain point in space, its function is simply superposition. This characteristic of light makes the light from all points of the object enter the camera lens without affecting each other, forming an image on the imaging plane.

(3) Law of Reflection of Light When light propagates to the interface of two different media, it will change the propagation direction and reflect the light. The law of light reflection states:

(1) The normals of incident light, reflected light and light projection points on the interface are in the same plane, and the incident light and reflected light are located on both sides of the normal respectively.

② The shooting angle and reflection angle are equal. The angle between the incident light and the normal n is recorded as the incident angle, which is expressed by I; The angle between the reflected light and the normal n is recorded as the reflection angle, which is expressed by α. Then i=α. The reflection of light is also reversible. If light is incident on the interface against the original reflected light, it will be reflected against the original incident light. According to different interfaces, reflection can be divided into directional reflection and diffuse reflection. Light is incident on a bright plane mirror from one direction, all incident points fall on the same plane, and all reflections are in the same direction, which is called directional reflection. When light is projected from one direction onto a rough surface (such as ground glass surface), because the rough surface can be regarded as composed of many facets with different angles, the light is reflected from different directions, which is called diffuse reflection. However, it should be noted that in the diffuse reflection phenomenon, every ray still follows the reflection law.

The reflection of light plays a very important role in photography. For example, people themselves do not emit light, but when light shines on people from all angles, it can be reflected from all angles. We often use reflected light to take pictures, which is to follow the reflection law of light.

3. Physics exists around physicists. Galileo, an observant Italian physicist, took great interest in the swing of the copper chandelier hanging in the air in Pisa Cathedral when he was attending church. Later, after repeated observation and research, he invented the synchronization of the pendulum. In order to understand the essence of "God's wrath", Franklin, an American physicist who is brave in practice, risked his life to bring "God's fire" to the world with an ordinary kite on a day of lightning, thunder and rain, and invented the lightning rod. British innovation scientist Henry? Achar went to the post office to handle affairs. At that time, a foreigner next to me took out a large edition of new stamps to cut and post on the envelope, but he didn't have a knife. I borrowed it from Aga, and Aga didn't have it. The foreigner had a brainwave, took off the pin on the suit and tie, neatly pierced a circle of holes around the stamp, and then neatly tore it off. When the outsiders left, they left Aga with a series of profound thoughts, and therefore invented the stamp punching machine, and the stamps with tooth patterns were born. Archimedes discovered Archimedes principle in ancient Greece; German physicist roentgen discovered x-rays; ..... There are countless examples of physicists who have made great achievements in studying trivial matters around them.

Physics also exists around students. After learning the basic knowledge of measurement, the students began to make soft rulers. A classmate is ingenious, wrapping the kraft paper soft ruler with transparent glue, which is more firm. Then a box wrapped in bubble gum is used as the shell of the soft ruler, the center of the box is made of iron wire, and the end of the soft ruler is fixed on the shaft, thus a tape measure that can be cleaned and reused is born. At the same time, inspired by the soft ruler, this student solved an exercise through experiments: when measuring the length of an object with a soft ruler, if the soft ruler is lengthened, is the measured value too large or too small? He did such a simulation experiment: draw a straight line on a white paper, mark it with a scale, then stick it with transparent glue, and then pull it down to make a "soft ruler". With the "soft ruler", he not only found the answer to the above questions, but also clearly saw that the graduation value became larger, and he knew why. After learning the knowledge of electricity, the students explored the maximum voltage that the earthworm can bear: when a voltage of 1.5V is applied to it, the earthworm quickly secretes mucus and struggles to jump out of the bottle. Earthworms are electrically divided into two parts when a voltage of 3V is applied. When measuring the power of "2.4V, 0.5A" small bulb and studying its luminous situation, some students are not satisfied with adding 2.4V voltage to the bulb, but do destructive experiments with their own small bulbs, and constantly increase the voltage at both ends of the bulb until the voltage reaches 9V, and the filament of the bulb burns out. When some students are learning the knowledge of evaporation, they take pains to sit at the table and observe the same two drops of water (one of which is flat), and then observe them carefully, and then analyze and compare them to get the factors that affect evaporation; ..... It is not uncommon for students to capture trivial things around them and explore.