1. Basketball tips

Dribbling: The key is to look at the rhythm. If you shoot it, pick it up, and shoot it again, it is a two-time dribbling violation (except for street ball, of course). Dribbling You can pass the ball faster or slower at key rhythms, such as when turning around. When changing direction, you can raise your hands and turn your hands slightly, and be fast (when dribbling, you must control the pace of your steps, and when encountering a stop where the defender can keep up with his footsteps, Keep your hands down and continue dribbling, and then look for opportunities to break through or shoot, don't blindly accelerate to break through)

Generally, when you first learn to dribble, shake before dribbling, cross-step, and side step==, and become proficient in dribbling behind the back, and crossing over. Dribble down, step down and turn around. Generally, when you stop dribbling the ball, you will make a fake move or shoot directly.

Taking off: Any jump is counted as a step, one foot is a step, and both feet land at the same time. Counting two steps (jump step)

3 steps to the blue: take two steps and the third step is to jump to the blue. You have to understand it as 3 steps. Hold the ball for two steps and then take off (you can’t stop in the middle) (Not counting walking)

2. Basic knowledge about the sea

1. Why is the sea water blue?

When the sun shines on the ocean, only the blue light is reflected back, while the other colors of light are absorbed by the seawater, so the seawater we see is blue.

2. Why is sea water salty?

When large and small rivers flow through the land, they absorb large amounts of salt from rocks and soil and carry this salt into the sea. So sea water is salty. We set up salt fields on the coast to slowly evaporate seawater, and then we can get sea salt. About 100 million tons of sea salt are produced around the world every year.

3. Why are there waves in the sea?

Seawater itself does not create waves. Waves are caused by the influence of wind, undersea earthquakes, or the attraction of the moon and sun. Among these factors, wind has the greatest influence on sea waves.

4. How big is the ocean?

If the earth's surface is divided into four parts, then three parts are covered by sea water, and only one part is land. The earth can be said to be a veritable water planet.

5. Can the sea breathe?

The phenomenon of sea water rising and falling on time is that the sea is breathing rhythmically, and it does so every day, year after year. Its name is "Tide".

The sea water is constantly rising and falling, containing huge energy. A wire cage filled with 12 tons of stones was once placed near the mouth of the Qiantang River, but it disappeared without a trace after a tide.

As early as 1912, the world's first tidal power station was built. Someone has calculated that if all the tidal energy on the earth is utilized, 1.24 trillion kilowatt-hours of electricity can be generated every year, which is equivalent to the power generation of 110 Gezhouba hydropower stations.

6. Why should we protect the ocean?

The ocean covers 71% of the earth and is the main source of freshwater runoff from continents. The vast water surface, huge water bodies and never-ending ocean currents regulate global temperature and precipitation. The ocean provides humans with 3 billion tons of fish every year. Algae products alone are 20 times more than the world's current total wheat production. The ocean's ability to provide food is 1,000 times that of land. The recoverable reserves of seabed oil are about 300 billion tons, which is 40% of the world's total oil reserves. Manganese (měng) nodules on the seafloor have been available to humans for tens of thousands of years. Seawater also contains a variety of nuclear materials such as uranium and hydrogen isotopes, as well as a large number of inorganic salts and other resources. The ocean also contains huge tidal energy, estimated to be more than 1 billion kilowatts. If wave energy and current energy are also taken into account, it will be even more impressive.

Uncontrolled pollution and predatory development will inevitably seriously damage mankind’s unique marine environment. Protecting the ocean is to protect the common environment of mankind and to protect the future of mankind. This has become people's common consciousness.

Why establish a marine nature reserve

The ocean is the cradle of life. More than 200,000 species of creatures still live there. According to statistics, there are 32 categories in the animal kingdom, 23 of which live in the ocean. However, with the development of science and technology, the scope of marine development and utilization continues to expand, which has brought some adverse effects to the marine natural environment and natural resources, and even caused serious damage. The most obvious thing is that fish resources in some sea areas have declined sharply, and some rare marine animals and plants are on the verge of extinction. This cannot but arouse people's great attention.

The establishment of a marine nature reserve can preserve the natural conditions of a part of the sea area that is not disturbed by humans, so that various marine life can be preserved and continuously used by humans. This has a great impact on the development and utilization of marine resources, scientific research, and culture. Education and tourism are both of great significance. Internationally, the construction of marine nature reserves is regarded as one of the standards for measuring the level and cultural level of a country's marine protection undertakings.

The ocean is not only very vast, but also surprisingly deep. At its deepest point, even if the entire Mount Everest, the tallest mountain in the world, were lowered, its top would be completely submerged by the sea water!

Just inside the vast and unfathomable ocean lies endless animals, plants, minerals and other resources. There are more than 150,000 types of marine animals that have been discovered so far, ranging from whales that are more than 30 feet long and weigh more than 120 tons, to zooplankton that are so small that they can only be seen with a microscope. The countless fish, shrimps, crabs, and clams (bàng) are all nutritious, delicious and delicious food. There are more than 10,000 species of algae and other marine plants, many of which are rich in fat, protein and vitamins indispensable to the human body. They can be used as excellent food or made into precious medicines. Deep in the seabed, the more important treasure is the abundant oil that people have found! All this is but a part of the wealth of this great secret storehouse of mankind. Since mankind's knowledge of the ocean is still shallow, there are still more treasures hidden deep under the sea, waiting for people to explore.

The Pacific Ocean is the largest, deepest ocean in the world with the most marginal seas and islands. Its maximum width is about 20,000 kilometers from east to west and about 16,000 kilometers from south to south, exceeding the combined area of ??all continents and islands. The average depth of the Pacific Ocean is 4,028 meters, and more than half are deeper than 5,000 meters. The deepest is the Mariana Trench, which is 11,034 meters deep. The Atlantic Ocean covers an area of ??93.36 million square kilometers and has an average depth of 3,626 meters. The deepest point is located in the Puerto Rico Trench, which is 9218 meters. The Indian Ocean covers an area of ??74.91 million square kilometers, with an average depth of 2,897 meters. The deepest point is the Java Trench, which reaches 7,450 meters. The Arctic Ocean covers an area of ??13.1 million square kilometers, with an average depth of 1,200 meters and a maximum depth of 5,449 meters.

3. Little knowledge about frogs

Little knowledge about frogs:

Frog (Frog) belongs to the amphibians of the phylum Chordata, class Amphibians, order Anura, and family Rana. Animals, adults are tailless, eggs are laid in water, fertilized outside the body, hatch into tadpoles, use gills to breathe, after mutation, adults mainly use lungs to breathe, and also use skin to breathe. Most frogs reproduce through in vitro fertilization, with fertilized eggs hatching into tadpoles outside the mother's body.

Frogs are slender and mostly good at swimming.

The neck is not obvious and there are no ribs. The ulna and radius of the forelimb are healed, and the tibia and fibula of the hindlimb are healed. Therefore, the claws cannot rotate flexibly, but the muscles of the limbs are well developed.

The most primitive frogs began to evolve in the early Triassic. The earliest jumping frogs today appeared in the Jurassic. Because frogs feed on insects and other invertebrates, they must live near water. There are about 130 species of frogs in China, and almost all of them are experts at destroying pests in forests and farmland.

Extended information:

Common frogs are:

1. Black-spotted frog

The black-spotted frog is a species of the family Ranaidae, with lateral folds. Amphibians of the genus Rana. The male of the black-spotted frog is slightly smaller, the head length is slightly longer than the head width, the snout is blunt and slightly pointed, the snout edge is not obvious, the forelimbs are short, the hind legs are short and plump, the tibia joint reaches the eyes in front, and the toes are almost fully webbed. The color of the back is dark green, yellow-green or brown-gray with irregular black spots, and the color of the abdomen is white without spots.

2. Rana limnocharis Boie

Rana limnocharis Boie (1834) belongs to the genus Rana of the family Rana and is a small frog. It is widely distributed in Southeast Asia. It is large in number and highly adaptable. It lives widely in fields, near ponds and hilly areas.

Widely distributed in Japan and Southeast Asia. In China, it is distributed in the plains and hilly areas south of the Qinling Mountains. It is also found in mountainous areas with an altitude of 2,000 meters. The most common and numerous.

3. Golden-threaded Frog

Golden-threaded frog refers to the golden-threaded side-pleated frog species group, including golden-threaded side-pleated frog, Fujian side-folded frog, and Hubei side-folded frog. species.

The golden-threaded frog belongs to the genus Pelophylax of the family Amphibidae and is an endemic species widely distributed in China.

The golden-threaded frog has a plump body, with an adult body length of about 50 mm (males are slightly smaller), a head length that is approximately equal to the width of the head, and a blunt and rounded snout. The tympanic membrane is large and obviously brown, and the temporal fold is not obvious. The back is green with some black spots and two long brown spots.

Sogou Encyclopedia - Frog

4. Why is the sky blue?

Isn’t the air in the sky colorless? Then why is the clear sky blue? , is there blue gas in the high sky?

No. On a sunny day, there are many tiny dust, water droplets, ice crystals and other substances in the air. When sunlight passes through the air, the longer wavelength red, orange, and yellow light in the sunlight can penetrate the atmosphere and directly hit the air. On the ground, blue, purple, indigo and other colors with shorter wavelengths are easily blocked by particles suspended in the air, causing the light to scatter in all directions and making the sky appear blue.

In fact, only a small part of the blue light is scattered. Most of the blue light and purple light that have not encountered particles are still directly emitted to the earth, so the white light emitted to the earth is still red, orange, and yellow. , green, blue, indigo, purple.

After a heavy rain, have you ever noticed that the sky becomes bluer? The clearer the weather, the bluer the sky. This is because of the amount of dust particles, droplets, and ice crystals in the air in such weather. There will be a lot.

5. Little knowledge about color modulation, the two colors can be mixed to become blue

Add an appropriate amount of cyan to magenta to get blue.

Blue is a color. It is one of the three primary colors of red, green and blue light. Among these three primary colors, its wavelength is the shortest, 440~475n nanometers, which is a short wavelength.

Blue is a symbol of eternity. There are many types of blue, each of which represents a different political or other meaning. In addition, there are many examples of music, books, and stars named after blue. .

Extended information:

The three primary colors of light are RGB (red, green and blue). The combination of these three colors, RGB, can form almost any color. The light will become brighter and brighter, and by mixing two or two, you can get a brighter intermediate color: yellow, cyan, magenta (or magenta, magenta). White can be obtained by combining three equal amounts.

Complementary color means that it does not contain another color at all. Red and green are mixed to form yellow. Because it does not contain blue at all, yellow is the complementary color of blue. Yellow is obtained when red and green are mixed in a certain proportion. So yellow cannot be called the three primary colors.

The colors we see in printing are actually the light reflected by the paper we see. For example, when we adjust colors when painting, we also use this combination. Pigments absorb light, not the superposition of light. Therefore, the three primary colors of pigments are the colors that can absorb RGB, which are cyan, magenta, and yellow (CMY). They are the complementary colors of RGB.

Baidu Encyclopedia-Three Primary Colors

Baidu Encyclopedia-Blue

Baidu Encyclopedia-Three Primary Colors of Light

6. Common sense in daily life

200 little tips in daily life 1. If you eat something spicy and feel like it will kill you, put a little salt in your mouth, hold it in your mouth, spit it out, and rinse it. If you put it in your mouth, it will not be spicy; 2. If your teeth are yellow, you can chew peanuts and hold them in your mouth, and brush your teeth for three minutes. It is very effective; 3. If there is a small area of ??skin damage or burns or scalds, apply a little toothpaste on it. It can immediately stop bleeding and relieve pain; 4. Often there are unsightly tea stains left in cups filled with tea, wash them with toothpaste and they will be very clean; 5. Open your mouth slightly when you nod eye drops, so that your eyes will not blink randomly; 6. Mouth If there is an ulcer in your eyes, just apply vitamin C to the ulcer, and the ulcer will be basically healed after it dissolves; 7. If there is small dust in your eyes, close your eyes and cough hard for a few times, and the dust will come out on its own; 8. After washing your face Finally, dip your fingers into some fine salt and rub it gently on both sides of the nose, then rinse with water. The blackheads and acne will be removed, and the pores will become smaller; 9. When you have just been bitten by a mosquito, apply it Soap will make it less itchy; 10. If your throat or gums are inflamed, cut the watermelon into small pieces at night and eat it with salt. Remember to do it at night, then the symptoms will be relieved and you will be fine the next day; 11. Blow the hair dryer on the label until the glue on the label is hot, and you can easily tear off the label; 12. If you are afraid of wrinkles when taking clothes with you on a trip, you can roll each piece of clothing into a roll; 13. Drink some vinegar when you burp, and you will see immediate results; 14. If you eat something with a peculiar smell, such as garlic and stinky tofu, just eat a few peanuts; 15. To treat coughs, especially dry coughs, use it before going to bed at night. Fry eggs with pure sesame oil, add a little more oil, don't add any seasonings, eat it while it's hot and go to bed, the effect will be obvious after eating it for a few days; 16. If a girl with thick wrists wants to wear a thinner bracelet, just Don't wear it hard. You should put a plastic bag on your hand and put on the bracelet. It is very easy to wear and will not hurt your hand. The same method is used to remove it; 17. Chestnut skin is difficult to peel, peel off the shell first, and then remove it. Put it in the microwave and spin it, take it out and rub it while it is hot, and the skin will fall off; 18. When arranging flowers, add a drop of dishwashing liquid to the water, which can last for several days; 19. Steam the walnuts in a pot After ten minutes, take it out and put it in cold water and then smash it open, and you can take out the complete peach kernel; 20. Put the shrimp into a bowl, add a little salt and edible alkali powder, rub it with your hands for a while, then soak it in water, and then Then rinse with water to make the fried shrimps as transparent as crystal, tender and delicious; 21. When frying meat, soak the meat in baking soda water for ten minutes, pour out the water, and then add the flavor, it will be very tender when fried. Slippery; 22. Soak the remaining tea leaves in water for a few days and then pour them on the roots of plants to promote plant growth; 23. Dry the remaining tea leaves and burn them in toilets or ditches to eliminate stench and repel mosquitoes and flies; 24. How to re-cook the rice with uncooked rice: Use chopsticks to poke some holes in the rice that go straight to the bottom of the pot, sprinkle a little rice wine and simmer again. 25. If only the surface is uncooked, just flip the surface layer to the middle and simmer again; 26. Remove the screen skillfully Grease: Put the remaining cigarette butts from washing clothes and smoking in water. After dissolving, use them to clean glass windows and screens. The effect is really good; 27. Just put a small piece of chalk in the jewelry box. It can keep the luster of jewelry; 28. The sticker traces on the surface of tables and bottles can be wiped with wind oil; 29. ??Always carry a small dry battery in the bag when going out. If the skirt has static electricity, put the positive terminal of the battery on the skirt. Just rub it on for a few times to remove the static electricity; 30. No matter which part of the shoe rubs your feet, just apply a little white wine on the place where the shoes rub your feet to ensure that it will not rub your feet; 31. When mixing vegetables, If it is necessary to blanch the vegetables, it is best to use the water used to blanch the vegetables as much as possible.

For example, when making dumplings, an appropriate amount of blanched water can be put into the meat filling, which not only ensures nutrition, but also makes the dumpling filling delicious and soupy; 32. Feet tend to sweat in summer, so use light water every day. Soaking your feet in salt water can effectively deal with sweaty feet; 33. Sunbathing after swimming in summer can prevent skin strain and other diseases; 34. Pillows are prone to moisture and mold breeding in summer, and frequent exposure to the sun is good for your health; 35. Eat more barley and adzuki bean porridge, etc. Moisture strengthens the spleen and can prevent heatstroke and dampness; 36. Prevent insomnia: talk less before going to bed, avoid drinking strong tea, do not use your brain before going to bed, and wash your feet with hot water and vinegar; 37. Honeysuckle has the effect of dispersing rheumatism. Decoction the juice and mix it with honey to relieve heat; 38. Drinking tea after eating too fatty food can stimulate the autonomic nervous system and promote fat metabolism; 39. Lack of sleep will make you stupid, and you need eight hours of sleep a day. , having a nap habit can delay aging; 40. Hands tend to become dry and rough, so soaking hands with vinegar for ten minutes can protect your skin; 41. In summer, wipe the mat with water added with toilet water to keep the mat fresh and clean. Of course, it is best to wipe along the lines of the mat so that the toilet water can penetrate into the lines and gaps of the mat, so that the cool and comfortable feeling will last longer; 42. Eat more tomatoes, citric acid and other acidic vegetables and fruits for breakfast, which is good for nourishing the liver; 43. Refreshing and antipruritic. When washing your hair or taking a bath, add five or six drops of toilet water to the water, which can have a good cooling and sterilizing effect, remove prickly heat and relieve itching; 44. Grapes contain sleep-auxiliary hormones, and regular consumption can help sleep; 45. Drinking more tomato soup in summer can not only obtain nutrients, but also replenish water. Tomato soup should be cooked and cooled before drinking. The lycopene contained in it has certain effects on resisting prostate cancer and protecting myocardium, and is most suitable for men; eating acidic foods Brushing your teeth immediately with substances will damage your dental health; 46. When the skin is broken due to trauma, apply toothpaste on the injured area to reduce inflammation and stop bleeding, and then bandage it. As a temporary first aid, medicated toothpaste has the most significant effect; 47. Spray white vinegar on the vegetables. Put it on the board and leave it for half an hour before washing it. It can not only sterilize but also remove odor; 48. Drinking yogurt can relieve irritability after alcohol. Yogurt can protect the gastric mucosa, delay alcohol absorption, and is rich in calcium, which is good for alleviating irritability after alcohol. Especially effective; 49. When the leather shoes and foreskins have been moldy for a long time, you can use a soft cloth dipped in alcohol and water (1:1) solution to wipe it; 50. When you have a headache or dizziness, you can apply toothpaste on your temples, because toothpaste contains menthol, Clove oil can relieve pain; 51. Freeze the candle for 24 hours before inserting it on the birthday cake. It will not shed candle oil when lit; 52. White clothes tend to turn yellow after being washed. You can take a basin of water and drop two drops of it on it. Three drops of blue ink, soak the washed clothes for a quarter of an hour, do not wring them out, just put them in the sun to make them white and clean; 53. Excessive consumption of raw onions and garlic will damage the mouth and stomach, which is bad for health. It is best to add a little vinegar before eating; 54. Replenish water in time but drink less fruit juice.

7. Tips on environmental protection

1. Wear light and keep cool when going out. Work clothes are mainly lightweight and energy-saving. It is estimated that the carbon reduction effect can reach more than 3,000 metric tons per year.

2. Use alternative energy, less oil and more alternative energy, such as solar energy, wind energy and natural gas, to help the earth increase sustainable energy!

3. Idling and turning off the engine when parked reduces exhaust gas, saving approximately 1.25 liters of fuel consumption per vehicle per year and reducing CO2 emissions by 2.7 kilograms.

4. Bring your own kettle and cup, which saves the cost of reusing a bottle 20 times and saves 1/3~1/4 of CO2 emissions.

5. Use recycled products and reduce pollution. The production process of recycled pulp can reduce tree felling and consume less energy, reduce air pollution by about 75%, water pollution by 35% and reduce a lot of of solid waste, recycling one ton of paper will save 242 kilograms of CO2.

Little knowledge about the ozone layer (1) As we all know, ultraviolet radiation from the sun is very lethal to living things. Fortunately, there is an ozone layer 25 – 50 kilometers above the Earth’s surface. Ozone is a trace gas in the Earth's atmosphere. It is a blue, radioactive gas composed of three oxygen atoms (O3) bonded together.

Replacing ordinary incandescent lamps with energy-saving lamps can save 70%-80% of electricity, and the lifespan of energy-saving lamps is more than 6 times that of ordinary incandescent lamps.

2. When electrical appliances are not in use, the power supply should be cut off to avoid standby energy consumption of remote control switches, continuous digital display, wake-up and other functional circuits, which account for about 10% of household electricity consumption, just like turning on a 15-watt to 30-watt lamp day and night.

8. Ten little pieces of knowledge about the ocean that are urgently needed

1. People often like to use blue to describe the ocean. In fact, the color of sea water ranges from dark blue to turquoise, from yellowish to brownish red, and even white and black, not just blue.

Seawater, like ordinary water, is colorless and transparent. The color of the ocean is determined by the optical properties of the seawater, the suspended matter contained in the seawater, the depth of the seawater, the characteristics of the clouds and other factors. As we all know, sunlight is composed of seven colors: red, orange, yellow, green, cyan, indigo, and violet. The wavelengths of these seven colors of light are different. From red light to violet light, the wavelength gradually becomes shorter, and the long wave passes through it. It has the strongest penetrating ability and is most easily absorbed by water molecules. Short wave has weak penetrating ability and is prone to reflection and scattering. Seawater absorbs, reflects and scatters light of different wavelengths to varying degrees. Red light, orange light, and yellow light with longer light waves are gradually absorbed as the depth of the ocean increases after hitting the sea water. Generally speaking, in the ocean with a water depth of more than 100 meters, most of the three wavelengths of light can be absorbed by the seawater, and can also increase the temperature of the seawater. When blue light and violet light with shorter wavelengths encounter purer seawater molecules, they will be strongly scattered and reflected, so the ocean that people see appears azure or dark blue. The seawater near the coast is mostly light blue or green due to the increase in suspended matter, larger particles, weak absorption of green light and strong scattering.

Purple light has the shortest wavelength and the strongest reflection. Why isn’t seawater purple? Scientific experiments have proven that human eyes have certain biases. Human eyes have a very weak sensitivity to purple light, so they are very insensitive to the purple reflected by sea water, and therefore turn a blind eye. On the contrary, human eyes are more sensitive to blue and green light. sensitive.

In addition, because the sun sometimes disappears in the clouds and sometimes shines through the clouds, the color of the ocean changes accordingly. The color of the ocean also depends on how high the sun is above the horizon.

2. Coal, oil, natural gas and other things that are found on land are basically available

3. Prokaryotes, protists, algae, mosses, ferns, a few angiosperms, and invertebrates Animals (except some arthropods), amphibian larvae, and some mammals

That’s basically it

9. Little knowledge about popular science

The physics of rainbows Principle Rainbow is a natural light phenomenon that people often see.

Whenever a colorful rainbow hangs in the sky, people can't help but rush to watch this natural beauty. In ancient times, some people said that it was the colorful silk that the lonely Chang'e sang and danced in the clouds; others said that it was the colorful bridge that fairies built in the clouds to peek into the world.

Whether it is colorful silk or colorful bridges, they are just magical legends. And what is a rainbow in reality? How did it form? When it comes to the formation of a rainbow, people often refer to it as.

After the rain. Connected.

Many people think only. After the rain.

Only then can a rainbow appear. In fact, this view is incomplete.

After the rain.

It is true that rainbows sometimes appear in the sky, but rainbows can also appear around fountains or waterfalls in the sun; in summer, sometimes a section of rainbow appears behind a sprinkler truck running on the street. Rainbow; spraying in the air with a sprayer can also form a rainbow... Apparently, that kind of rainbow only exists.

After the rain. The reason why rainbows appear is because the causes of rainbows are not fully understood.

As long as you know that the conditions for rainbow formation exist in the air, you will naturally know that it does not have to rain for a rainbow to appear. In middle school physics class, there was this.

The dispersion of light. Experiment: Take a prism and let a beam of white light pass through the slit and hit one side of the prism. After passing through the prism, its direction changes and a colored light band is formed on the white light screen. The order is red, orange, yellow, green, and blue. , indigo, purple seven colors.

This is similar to the colors of the rainbow. But it is impossible for a prism to form a rainbow in the air.

Why is this? This is because there are lots of small water droplets floating in the air.

When sunlight shines on these small water droplets, each small water droplet acts like a prism to decompose the white light into seven monochromatic lights, which plays a role in spectral dispersion of the sunlight.

How does sunlight produce spectral dispersion in small water droplets? When sunlight enters a small water droplet, that is, from a medium like air into a medium like water, a refraction occurs. Due to the different refractive indexes of the various monochromatic lights that make up white light, purple light has the shortest wavelength and the largest refractive index, while red light has a longer wavelength. , its refractive index is the smallest, and the other colors of light are in between. Therefore, the light splits in the small water droplet. The light of various colors continues to propagate in the small water droplet at the same time. When it encounters another interface of the water droplet, it is reflected back, passes through the inside of the small water droplet again, and is refracted back to the air when it comes out.

In this way, sunlight is decomposed into seven monochromatic lights of red, orange, yellow, green, blue, indigo and violet after two refractions and one total reflection in the small water droplets. When there are a lot of small water droplets in the air, the sunlight passes through these small water droplets, and after reflection and refraction, the light emitted is concentrated together, and a beautiful rainbow is formed in the sky.

Usually, most of what we see is a rainbow, with a viewing angle (from the ground to the top of the rainbow) of about 42°. Sometimes you can see another rainbow outside the rainbow with the exact opposite color sequence and darker color. This is called a secondary rainbow.

The main rainbow is inner ultraviolet red, and the secondary rainbow is inner infrared purple. The secondary rainbow is also called neon. The neon and the main rainbow are concentric arcs. The sky between the two is darker, while the sky inside and outside the rainbow is brighter.

Ni's viewing angle is approximately 51°. Its causes are basically the same as those of the main rainbow.

It is formed by sunlight in small raindrops after two reflections and two refractions, that is, refraction-total reflection-total reflection-refraction. On the ground plane, the main rainbow and neon we see are semicircular, because their lower parts are covered by the ground.

If you stand on the top of a high mountain, you can see most of the main rainbow and neon. Only on a clear day, looking down in the airplane cabin, can you see the full picture of the main rainbow and neon, that is, the complete circle.

If the angle of the sun is too large (for example, around noon), or too small (near sunrise or sunset), it is difficult for us to see a rainbow, because rainbows are sunlight reflected by small water droplets and enter our eyes. , so the rainbow always appears on the opposite side of the sun, therefore. Morning rainbows are seen in the west, and evening rainbows are seen in the east.

It mainly appears in summer.

Why is the main rainbow internally ultraviolet red? When we look at the rainbow, colored light is reflected from small water droplets at various angles. For a certain particle, only one color of light can be emitted into us. our eyes, while other colored lights refracted from the same raindrops pass higher or lower beyond our eyes and are not seen by us. Specifically, among the light refracted by the small water droplets that can enter our eyes and are at the highest position, red light has the smallest refractive index and the smallest deflection angle, so it can enter our eyes. What we see Only red light and other colored lights pass over our heads due to their large refractive index and large deflection angle.

The slightly lower water droplets can only enter our eyes first and be seen by us because the deflection angle of the refracted light is larger than the red light and smaller than the other colors of light. Among the other colors of light, red light is on the low side, while yellow, green, blue, indigo and violet are on the high side and cannot be seen by us beyond our eyes.

By analogy, for the light that enters our eyes and is refracted by the small water droplets at the lowest level, we can only see purple light, and the other colors of light slip away from under our eyelids. In this way, the light refracted from adjacent small water droplets in the air forms a rainbow of inner ultraviolet and red.

Meteorological principles of rainbows The size of water droplets in the air determines the color and width of the rainbow. The larger the raindrop, the narrower the rainbow band and the more vivid the color; the smaller the raindrop, the wider the rainbow band and the darker the color.

When the raindrops are small enough, the light splitting and reflection are not obvious, and the rainbow disappears. This shows that the formation of rainbows is directly related to the existence, number, and size of raindrops in the air. In turn, rainbows are related to weather changes.

For example: If the color of the rainbow changes from bright to dull, and the width changes from narrow to wide, it means that the raindrops in the air gradually become smaller. From this, we can speculate that the air may gradually become stable and the weather may gradually change. The situation is gradually stabilizing.