Know little about light science.

Why do sunflowers always face the sun? Sunflower stems contain a wonderful auxin.

This auxin is very afraid of light. When it is illuminated, it will go to the backlight side, and the cells on the backlight side will multiply rapidly. Therefore, the backlit side will grow faster than the bright side, which will bend the sunflower to light.

2. Why do the stars twinkle? We see the stars shining, not because the luminosity of the stars has changed, but because of the occlusion of the atmosphere. The atmosphere is between us and the stars. When starlight passes through the atmosphere, it will be affected by the density and thickness of the atmosphere.

The atmosphere is not absolutely transparent, and its transparency will change according to its density. So when we look at the stars through it on the ground, we will see that the stars seem to be flashing.

3. Why do people yawn? When we feel tired, a lot of carbon dioxide has been produced in our bodies. When there is too much carbon dioxide, oxygen must be supplemented to balance the needs of the body.

Because these residual carbon dioxide will affect our body's functional activities, then the body will send out a protective reaction, so we yawn. Yawning is a deep breathing action, which will let us breathe in more oxygen and expel more carbon dioxide than usual, and it can also eliminate fatigue.

How high is the blue sky? "Blue sky" is actually the earth's atmosphere. The atmosphere surrounds the earth's air and is divided into five layers according to the air density, with a total thickness of 2000-3000 kilometers.

But most of the air is concentrated below 15 km from the ground, and the higher the air, the thinner it is. How thick the atmosphere is, how high the blue sky should be.

5. Why are there no stars in the daytime? Because part of the sunlight is scattered by the gas and dust in the atmosphere during the day, the sky is very bright and the light radiated by the sun is so strong that we can't see the stars. 6. What celestial bodies are there in the solar system? There are nine planets in the solar system.

They are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. In addition, there are many asteroids, comets and meteors in the solar system, and there are 2958 officially numbered asteroids.

The most famous comet is Halley's comet. 7. Why does it thunder? This is a natural phenomenon that negative electricity meets positive electricity.

When it rains, some clouds in the sky are positively charged and some are negatively charged. When two clouds meet, they will discharge, emit bright and bright lightning, and at the same time release a lot of heat, which will make the surrounding air heated, expand and make a loud noise. This is thunder. 8. Why can an airplane fly into the sky? This plane has two wings, like those of a bird. It has a propeller.

The wing can generate lift and lift the plane into the air; Propeller can produce the ability to push the plane forward. Therefore, the plane can fly into the sky like a bird.

33. For a quartz clock hanging on the wall, when the battery runs out and stops, its second hand often stops at the position of "9" on the dial. This is because the second hand is most hindered by the large torque at the "9" position.

9. Before the water boils, the bubbles in the water rise and vibrate up and down due to convection. Most of the bubbles burst under the pressure in the water, and their cracking and vibration sound together with the container produce a * * * sound, so the sound is very loud. After water boils, it is isothermal up and down, and the bubble volume increases. Under the action of buoyancy, it will explode when it reaches the water surface, so the noise is relatively small.

10. Fire-water incompatible substances must reach the ignition point when burning. Because of the large specific heat of water, water can absorb a lot of heat when it comes into contact with fire, thus reducing the temperature of ignition materials; At the same time, the vaporized water vapor surrounds the burning object, making it impossible for the object to contact with air. Without air, combustion cannot be carried out. 1 1. Sit on the ground and walk for 80,000 days. Because the radius of the earth is 6370 kilometers, every time the earth makes a circle, the distance that objects on its surface "walk" is about 40003.6 kilometers, about 80000 miles.

This is a poem sung by * *, which also scientifically reveals the relationship between motion and stillness-motion is absolute, and stillness is always relative to the reference object. 12. According to the principle of lever balance, if the power arm is a fraction of the resistance arm, then the power is several times the resistance.

If the weight of the arm is very large, it is entirely possible to "dial one or two kilograms." 13. When the distance between molecules is large (more than several hundred angstroms), the attraction between molecules is very small, almost zero, so it is difficult to reassemble a broken mirror.

14. If the directions of the components are the same, the resultant force is equal to the sum of the components. 15. Tofu can't be hung with hemp rope. When the pressure is constant, if the stress area is small, the pressure will be great.

16. True gold is not afraid of fire, and truth is not afraid of argument. Judging from the melting point of gold, although it is not the highest, it is 1068℃, while the temperature of general flame is about 800℃. Because the temperature of the flame is lower than the melting point of gold, gold cannot be melted. 17. With a long whistle, people in the valley should give a long whistle. After many reflections, the sound can form a loud echo, which lasts for a long time. As if the mountains were shouting and the valleys were echoing.

18. Looking at the sky from the well, you can see very little. Because light travels along a straight line, from the knowledge of geometric drawing, the frog's field of vision will be very small. 19. It can be seen from the pressure formula that when the pressure is constant, the smaller the stress area, the greater the pressure.

People will feel very uncomfortable sitting on such a blanket. 20. Good years are bright. Because snow is a bad conductor of heat, when it covers crops, it can well prevent heat conduction and air convection, so it can play a role in heat preservation.

2 1. It is cold before frost and cold after snow. In the late autumn night, the temperature near the ground suddenly turns cold (the temperature is below 0℃), and the water vapor in the air condenses into small ice crystals and adheres to the ground to form frost, so it feels "cold before frost". When snow melts, it needs to absorb heat to reduce the temperature of the air, so we have the feeling of "cold after snow".

22. Eggs touch stones-overreached eggs touch stones. Although the force is the same, the pressure that each object can bear is certain. If this limit is exceeded, the object may be damaged. Eggs can withstand less pressure, so they will break.

23. Before the jade is polished, the surface is uneven and the light is diffuse. After the jade is polished, the surface is smooth and the light is mirrored. 24. Fans have a cool breeze, which is suitable for summer but not for winter.

2. About 20 words of scientific and technological knowledge.

3. Why can snakes walk without feet? Can a snake walk without feet? A snake has many scales on its body, which is the outermost layer of armor. Scales are not only used to protect their bodies, but also can be their "feet". When a snake crawls forward, its body will be S-shaped. Every scale except the S-shape will be tilted to help the snake grasp the uneven road when it moves forward. These scales cooperate with the muscles of snakes and can push their bodies to crawl forward, so snakes can walk without feet! 4. Why do sunflowers always bloom towards the sun? There is a substance called "auxin" in the stem under the sunflower disk. This substance has the function of accelerating replication, but it is anti-optical, and it will run to the backlight side whenever it encounters light. So when the sun rises, the stem of sunflower will immediately hide to the side of the backlight, and it seems that the whole plant is bent towards the sun. 5. Why do people get old? When people get old, their hair will turn white. There is a substance called melanin in our hair. The more melanin, the darker the hair will be. Without melanin, hair will turn yellow or white. When human beings reach old age, various functions of the body will gradually decline, and the formation of pigments will be less and less, so the hair will gradually turn white! 6. Why do fireflies glow? Can fireflies shine? Fireflies emit light because there is a luminous body at the end of their abdomen, which is filled with a lot of phosphorus-containing luminescent substances and luminescent enzymes, so that fireflies can emit flashing light. Fireflies shine not only for lighting, but also for courtship, vigilance, trapping and other purposes. This is also a communication tool for them. Different kinds of fireflies emit light in different ways, frequencies and colors, so they can convey different information. 7. Why are they hungry? Do you growl when you are hungry? When you are hungry, you will purr. This is because the food you have eaten before has almost been digested. Although the stomach is empty, the gastric juice in the stomach will continue to secrete. At this time, the contraction of the stomach will gradually expand, and the liquid and gas inside will stir up and make a purring sound. Don't be embarrassed by the growling of your stomach next time! Because this is a normal physiological action. 8. Why can't ostriches fly? Can't ostriches fly? A giant ostrich, but they can't fly into the sky! This is not because their wings are useless, but because their feathers are too soft and their wings are too small to fly at all. In addition, the ostrich's muscles are underdeveloped and its sternum is flat, which is not conducive to flying. Ostrich has lived in Africa for a long time, and in order to adapt to the environment, its body has gradually evolved into what it is now. 9. Why can't the food in cans go bad easily? Isn't the food in cans easy to go bad? Lunch meat, black beans, tomato sauce beans.

They are all delicious canned food, which can be preserved for a long time without deterioration. This is because the can is sealed and bacteria can't get in. When people make canned food, they pump out all the air inside and seal it. Without air, even if the food inside is stained with a little bacteria, they can't survive or reproduce! 10. Why do babies always cry at birth? Do babies always cry when they are born? Babies cry when they are born, not because they are unhappy, but because they are taking the first breath of air! When babies leave their mother's body and are born, the first breath of air will rush to their throats, violently impact the vocal cords, make them vibrate, and then make a sound similar to crying.

3. 50 little scientific knowledge around you

Science is everywhere. Here are 50 scientific tips 1.

Why do you see lightning first and then hear thunder? Light waves travel faster in air than sound speed by 2. Who was the first Olympic champion in China? Xu Haifeng III.

Who invented glasses? Roger? Bacon 4. Why does the bicycle move? Bicycle tires rub against the ground.

Whose title is the following? Poet Fairy-Li Bai, Poet Saint-Du Fu,-Li He, Poet Bone-Chen Ziang, Poet Crazy-He 6. What does the moon revolve around? How long does it take to make a revolution? Earth, 27.32 days 7.

What are the three plains in China? Northeast Plain, North China Plain, Middle and Lower Reaches of the Yangtze River Plain. How many earthquakes are there on the earth every year? About 5 million times.

What is the smallest and coldest star in the solar system? Pluto 10. What is the thickness of the earth? Atmosphere 1 1.

Why are there black boxes on the plane? It is used to record all kinds of situations on the plane during the crash and help people understand the cause of the accident. What are the customs during the Spring Festival? Sweep the house, set off firecrackers, put up Spring Festival couplets, eat New Year's Eve, etc. 13.

What animal can predict earthquakes? Cattle, horses, rabbits, chickens, ducks, dogs, snakes, rats, fish, etc. What plant blooms first and leaves later? Chimonanthus praecox, kapok, forsythia suspensa, peach tree, winter jasmine, pear tree, silver willow, bauhinia, Xiang Jie, Lycoris radiata and plum blossom 15.

How do bees make hives? Every worker bee has a wax gland at the waist, which can secrete wax. This wax becomes soft and tough after chewing in the mouth, and can be used to build a honeycomb. Why is the medicine bottle so light? Because light color can reflect light, dark color absorbs more light when exposed to sunlight, so drugs are easy to deteriorate.

Who invented the steam engine? Watt 18. Which dinosaur is the hardest? Stegosaurus 19.

What is the blood of the earth? Magma 20. What is the skeleton of the earth? Rock 2 1

Why not watch welding sparks? It contains ultraviolet rays harmful to the eyes. Why can't you turn off the lights and watch TV? The screen and image of TV are relatively small. In the dark, the vision should be highly concentrated and expanded, and it is particularly sensitive to the strong reflection of light on the TV screen, which will make the eyes suffer from * * * and the vision will drop by 23%.

Who are the top ten marshals of China people? Zhu De, Peng, He Long, Chen Yi, Liu Bocheng, Luo Ronghuan, Xu, Nie, Lin Biao, ** 24. Write down the dynasties in ancient China in order. Xia, Shang, Zhou, Qin, Han, Sui, Tang, Song, Yuan, Ming and Qing 25.

Why don't rabbits need water? Because the rabbit's staple food vegetables contain a lot of water, which is enough for the body. If there is more water in the intestine, you will get gastroenteritis. But rabbits can drink water when they are short of water.

What is a meteor? It refers to meteoroids running in interstellar space (usually including cosmic dust particles and solid blocks), which are attracted by the earth due to the perturbation of the earth's gravity when approaching the earth, and then enter the earth's atmosphere and burn with it. List some outstanding astronomers in the history of China.

Zhang Heng and his party, Guo Shoujing and Li, 28 people. Who is the inventor of the battery? Volt 29.

Where is Mount Vesuvius? Italy. 1 who are the two astronauts who arrived at the moon? Armstrong and Aldrin 3 1.

Which province and city is Mount Tai in? Taishan City, Shandong Province 32. Which countries does the Amazon River flow through? Brazil, Peru and Colombia.

Which countries does the Irrawaddy River flow through? China, Myanmar. What are the five most precious gems in the world? Diamonds, sapphires, rubies, emeralds and opals.

What was the name of the ancestor of the fish? Amphioxus 37 What kind of fish glows? Ankang fish, snapper, dragon head fish, naked eye fish, etc.

How many muscles does a person have? A * * * has more than 600 muscles. Will all the wood float on the water? No, there is a kind of "steel tree" that won't float on the water.

What is the biggest flower? Dawanghua 4 1. Who invented anesthesia? Hua tuo 42.

What is the capital of France? Paris 43. What is the capital of England? London 44.

What is the capital of Japan? Tokyo 45. What is the capital of Italy? Rome 46.

What is the capital of the United States? 47 Washington. What bird is one of the ancestors of birds? Archaeopteryx 48.

What are the four seafood products in China? Pseudosciaena crocea, Pseudosciaena crocea, hairtail, squid. What is the largest mammal? Blue whale 50.

What is the largest amphibian? giant salamander

4. Encyclopedia of scientific and technological knowledge

What are the three parts of sunlight? Among the eight planets, Jupiter is the largest freshwater lake in China and the first of the five mountains in Poyang Lake. The rotation of Mount Tai passes through the north and south poles around the earth's axis, and the direction is from west to east. The farther away from the poles, the faster the speed. The largest mammal in the world is the blue whale. Which city is called the foggy capital of the world? 2 1 what is the main energy source in London in the century? What kind of pollution is called windmill power generation kingdom in Denmark? What kind of pollution is called the world's number one killer? Which country's Mercury Green Mud Observatory is the closest planet to the sun? Dry ice in Britain is carbon dioxide. Bi Sheng of China invented movable type printing in the Northern Song Dynasty. It is also a maritime power. With a vast territory of 9.6 million square kilometers, China is the largest country in Asia and one of the largest countries in the world, ranking third in the world after Russian and Canadian countries.

The coastline of Chinese mainland starts from the mouth of Yalu River in the north and ends at the mouth of Beilun River in the south, with a total length of18,000 kilometers and an island coastline of more than 32,000 kilometers. There are more than 6,500 islands; According to the relevant provisions of the United Nations Convention on the Law of the Sea and China's proposition, the sea area under the jurisdiction of China is about 3 million square kilometers. China has vast sea areas and abundant resources, so China is also a maritime power.

Why is space junk so harmful? They have become potential killers of satellites and orbiting space stations, seriously threatening the safety of astronauts. You know, space junk runs at the speed of the universe.

An oncoming metal particle with a diameter of 0.5 mm is enough to pierce the sealed flight suit; Dust that people can't distinguish with the naked eye (such as paint chips and paint powder) can also kill astronauts; A fragment the size of an aspirin tablet can "paralyze" a satellite and send a spacecraft costing hundreds of millions of dollars into a dead end. Because of the huge amount of tiny space debris, it will seriously change the surface performance of spacecraft; Slightly larger space debris will damage the surface materials of spacecraft, cause impact pits and damage surface devices; The high-speed impact of space debris will vaporize itself and the surface material of the spacecraft being hit into plasma clouds, which will eventually lead to the failure of the spacecraft.

Interesting technology once, Newton was so absorbed in his experiment in the laboratory that he forgot the time to eat. His assistant took some eggs and sent them to the laboratory. He said to Newton, "Here are some eggs. Do it yourself. "

Newton said, "OK, thank you. Please put the eggs there. " After that, he immersed himself in the experiment.

After a long time, Newton was hungry and remembered that he hadn't had lunch yet. So, he took a small pot, put the eggs in the pot, put them on the stove, and began to do experiments again.

Half an hour later, Newton finished the experiment. At this moment, he remembered the eggs in the pot.

He opened the lid and found there were no eggs in it, only a pocket watch. Newton was surprised and looked up. The eggs are still on the table, but the pocket watch on the table is missing.

It turned out that Newton was absorbed in the experiment and cooked the pocket watch as an egg. 1, who knows how the sea freezes? Everyone thinks that the sea water is salty and won't freeze.

In fact, after the temperature is lowered, the solubility of water will also decrease, that is, salt will be precipitated. In this way, the water freezes.

2. Who knows if Altair has it now? What we are seeing now is the "light" it gave off a long time ago. As for whether it exists now, only people in the Altair galaxy know that the light we observe from the earth is still the light from a stable star.

In addition, the average life span of stars exceeds 6 billion years. So now the solar cell phone battery that Altair should still exist has come out. This kind of battery is a combination of ordinary lithium battery and other solar cells. Technicians stick a thin layer of crystalline silicon photoelectric conversion sheet on the back of lithium battery. Single crystal silicon receives the current generated by illumination and charges the lithium battery through the protection circuit. In fact, as long as there is light outside the sun, the solar cell phone battery can be automatically charged, and no matter how long the exposure time is, it will not be overcharged because of the holding circuit.

Although it is introduced, this battery can generate 1 minute of electricity when exposed to the sun for 5 minutes, and it can also be used for two or three days when exposed to a desk lamp for one night. In addition, this kind of battery also has the function of ordinary mobile phone battery. If the light is weak, you can use the mobile phone charger to charge.

Sandstorm Sandstorm is a disastrous weather phenomenon in which wind and sand interact. Its formation is closely related to global greenhouse effect, El Nino phenomenon, sharp decline of forests, vegetation destruction, species extinction, climate anomalies and other factors. Among them, overexploitation, excessive logging and excessive reclamation of natural resources caused by population expansion are the main reasons for sandstorms.

As a kind of high temperature disaster, sandstorm does not happen in all windy places. Sandstorms only occur in areas with dry climate and sparse vegetation. * * * The topsoil of the land is easily rolled up by a big storm to form a sandstorm or even a strong sandstorm. Sandstorms do no less harm to people and buildings than typhoons and tornadoes.

Recently, sandstorms have appeared in northwest and even northeast China, especially in northwest China, which has been hit by sandstorms for more than 20 times. Why is the air by the sea so fresh? The waves constantly beat the coast every day, and the tides rise and fall, bringing beautiful scenery, pleasant waves and humid coastal air to the coastal area.

The air in the seashore contains a lot of negative oxygen ions, which are called "air vitamins". They can enter the human body through breathing, improve the ventilation function of the lungs, and increase the inhalation of oxygen and the exhalation of carbon dioxide. In urban public places, negative oxygen ions 10-20 per cubic centimeter, indoor 40-50, green lawn 100-200, and coastal 100000, which are hundreds of times more than indoor ones! Negative oxygen ions are negatively charged ions, which have bactericidal effect and can inhibit the reproduction of bacteria in the air.

A large number of negative oxygen ions improve the function of human sympathetic nerve, make people refreshed and energetic, and also increase the content of hemoglobin in blood. Therefore, there are many sanatoriums on the seashore, because the seashore air has a therapeutic effect on people suffering from emphysema, hypertension, neurasthenia, asthma, anemia and other diseases, which is beneficial to human health and makes people refreshed.

About 5.20 words of scientific knowledge. Thank you.

Small scientific knowledge

Why does sorbet get angry?

The reason why sorbet bubbles is because there is a lot of invisible water vapor in the outside air. When it comes to cold sorbet, it will liquefy into droplets when it is cold. It seems that the sorbet is bubbling.

Why do sunflowers always face the sun?

Sunflower stems contain a wonderful auxin. This auxin is very afraid of light. When it is illuminated, it will go to the backlight side, and the cells on the backlight side will multiply rapidly. Therefore, the backlit side will grow faster than the bright side, which will bend the sunflower to light.

Why does cicada shed its skin?

Cicada's shell (exoskeleton) is hard and can't expand with the growth of cicada. When the cicada grows to a certain stage, the cicada's exoskeleton restricts its growth, and the cicada loses its original exoskeleton, which is cicada slough.

6. Encyclopedia of scientific knowledge (30 words)

Scientific common sense in life:

1. Why does sorbet get angry?

The reason why sorbet bubbles is because there is a lot of invisible water vapor in the outside air. When it comes to cold sorbet, it will liquefy into droplets when it is cold. It seems that the sorbet is bubbling.

2. Why do sunflowers always face the sun?

Sunflower stems contain a wonderful auxin. This auxin is very afraid of light. When it is illuminated, it will go to the backlight side, and the cells on the backlight side will multiply rapidly. Therefore, the backlit side will grow faster than the bright side, which will bend the sunflower to light.

3. Why do cicadas shed their skin?

Cicada's shell (exoskeleton) is hard and can't expand with the growth of cicada. When the cicada grows to a certain stage, the cicada's exoskeleton restricts its growth, and the cicada loses its original exoskeleton, which is cicada slough.

4. How do bees make honey?

First, the bees spit the sweet juice of the flowers they picked into an empty hive. At night, they suck sweet juice into their honey stomachs to make it, and then spit it out and swallow it. It takes 100~240 times to make sweet honey.

5, hanging on the wall of the quartz clock, when the battery runs out and stops, its second hand often stops at the "9" position on the dial. This is because the second hand is most hindered by the large torque at the "9" position. Scientific common sense

6. Sometimes, when tap water flows from the adjacent faucet, it occasionally makes bursts of noise. This is because the water pipe vibrates when the water rushes out of the tap.

7. When taking pictures on TV, turn off the camera flash and indoor lighting to make the picture clearer. Because the reflected light of the flash lamp and the illuminating lamp on the TV screen will interfere with the transmitted light of the TV picture.

8. At the same temperature, frozen meat thaws faster in water than in air. At the same temperature, hot nails cool faster in water than in air. A cup filled with boiling water cools faster when immersed in water than when immersed in air at the same temperature. All these phenomena show that water has better heat transfer performance than air,

9. When there is cold water in the pot, the water droplets attached to the outer surface of the pot bottom can only be dried up after a long time on the flame, and will only boil when it is dried up. This is because the water droplets, the pot and the water in the pot keep heat conduction, and the temperature is almost the same. As long as the water in the pot is not boiled, the water droplets will not boil, and the water droplets will evaporate on the flame and be gradually dried up.

10, out-of-shape mirror, the farther away from the mirror, the more out of shape. Because the image in the mirror is formed by the reflection of the silver-plated surface behind the mirror, uneven silver-plated surface or uneven glass thickness will lead to aliasing. The farther away from the deformed mirror, the more the reflected light on the silver-plated surface deviates from the normal position according to the principle of light amplification, and the more deformed the mirror is.