Causes and phenomena of mirage

Mirages are closely related to the geographical location, geophysical conditions and meteorological characteristics of those places at a specific time. The abnormal distribution of temperature is the meteorological condition for the formation of most mirage.

Take the formation of summer flies as an example. In summer, when the sun burns in the desert, the sand is burnt. Because of the small specific heat of sand, the temperature of low-level air near sand rises rapidly, while the temperature of high-level air is still very low, thus forming an abnormal distribution of temperature. Due to thermal expansion and contraction, the density of hot air in the lower layer near the sand is small, and the density of cold air in the upper layer is large, so that the refractive index of air is small and the air in the upper layer is large. When the light reflected by a distant higher object enters the sparse air in the lower layer from the dense air in the upper layer, it is constantly refracted, and its incident angle gradually increases, which is equal to the critical angle, and total reflection occurs. At this time, if people look against the reflected light, they will see the cockroaches below.

Because of the dark color of asphalt pavement, it has strong absorption ability in the hot summer sun, and it will also form the distribution characteristics of cold and dense upper air and hot and dense lower air, so it will also form underflow.

A mirage in the desert is the refraction of sunlight when it meets air with different densities. In the desert, the sand is baked by the sun during the day, and the temperature on the surface of the sand layer rises rapidly. Due to the poor heat transfer performance of air, when there is no wind, the vertical temperature difference over the desert is very significant, with high air density in the upper layer and low air density in the lower layer. When sunlight enters the low-density air layer from the high-density air layer, the speed of light changes, and after the refraction of light, the oasis in the distance appears in front of people. On the sea or river, this kind of "mirage" phenomenon happens from time to time.

A mirage is an optical illusion, a virtual image formed by the refraction of light reflected by objects on the earth through the atmosphere. Phantom is a mirage for short. According to the principle of physics, a mirage is because different air layers have different densities, and the refractive index of light in air with different densities is different. That is, because the density between warm air on the sea surface and cold air in the high air is different, it refracts light. Mirages are closely related to the geographical location, geophysical conditions and meteorological characteristics of those places at a specific time. The abnormal distribution of temperature is the meteorological condition for the formation of most mirage.

000 "Reasons for the Formation of Mirages"

Sailing on the calm sea or overlooking the seaside, you will often see images of distant ships, islands or towers reflected in the air; People who travel in the desert sometimes suddenly find a lake in the desert in the distance, and the shadow on the lake is swaying, which is desirable. But a gust of wind came and these scenes suddenly disappeared. It turns out that this is a mirage, commonly known as a mirage, or a mirage for short.

Phantom diagram

Why is this happening? To answer this question, we must start with the refraction of light.

When light propagates in a uniform medium with the same density, the speed of light is constant, and it propagates in a straight line. However, when light obliquely enters another medium with different density, the speed of light will change and the propagation direction will be tortuous. This phenomenon is called refraction. When you insert a straight rod obliquely into the water, you can see that the underwater part of the rod and its exposed part seem to be broken, which is the result of light refraction. Someone once used a device to project light from water to the interface between water and air. You can see that light is divided into two parts at this interface: one part is reflected into water and the other part is refracted into air. If the mirror in the water is rotated to make the light incident on the interface more inclined, then the refraction of light in the air will be more intense. When the light incident on the interface is shown in the figure on the left, all the light is reflected into the water, and no light is refracted into the air. This phenomenon is called total reflection.

Air itself is not a homogeneous medium. Generally speaking, its density decreases with the increase of height. The higher the height, the smaller the density. When light passes through the air layer at different heights, it will always cause some refraction, but this kind of refraction phenomenon has become accustomed to our daily life, so we don't feel anything strange.

In summer, the humidity of seawater is relatively low during the day, especially on the sea surface where cold water flows, and the water temperature is even lower. The low-level air is affected by the water temperature, which is colder than the high-level air, resulting in the abnormal phenomenon of cooling and heating (under normal circumstances, the average temperature drops by about 0.6℃ for every rise of 100m). Because the air pressure in the lower air layer is very high, and now the temperature is lower than that in the upper air layer, the difference between density and rareness under the air layer is extremely significant.

If there is a ship under our eastern horizon, it is usually invisible. If the difference between dense air and thin air is too big at this time, the light from the ship will gradually refract from the dense air layer to the thin air layer, and then return to the dense air layer below after total reflection in the upper layer; After such a curve, it finally enters our eyes and we can see its image. Because people's vision always feels that objects come from a straight line, the ship image we see is much higher than the real thing, so it is called a mirage.

There is a miaodao islands in Bohai Sea, China. In summer, the sea water temperature is low during the day, and the air density will be significantly different between underground density and sparse density. In Penglai County (called Dengzhou in ancient times) on the south bank of Bohai Sea, you can often see the phantom of miaodao islands. In the Song Dynasty, Shen Kuo recorded this in his famous Meng Qian Bi Tan:

"When you are in Zhangzhou Sea, there are clouds, such as watching the palace, the people in the city, and the crown of horses and chariots." This is a mirage he saw in Penglai.

1624 (May 2, 20041day) On July 6, a mirage occurred in Dengzhou, lasting more than 7 hours. Yuan Keli, the outgoing governor of Denglai, witnessed the whole process and was very excited. A poem "Poems on Haicheng" recorded the grand occasion at that time in detail, with beautiful words, which can make people who have never seen Haicheng feel immersive. 1In the early morning of May 22, 933 1 1 point, a mirage was also found on Zhucha Island in Qianhai, Qingdao (the outer mouth of Jiaozhou Bay), which spread all over the city for a time and many people went to watch it. 1975, a 6-hour mirage appeared in the sea near Guangdong province.

Mirages can be seen not only on the sea in summer, but also on the river sometimes. For example, 1934 appeared on the river near Nantong on August 2. It was cold that day, and it was particularly hot. In the afternoon, I suddenly found balcony walls and tree houses over the Yangtze River, both of which are more than 20 miles long. About half an hour later, it moved eastward and suddenly disappeared. Then three mountains appeared, towering into the sky, with a mountain in the middle, much like a censer; It took half an hour to disappear.

In the desert, the sand is scorched by the sun during the day, and the temperature near the sand layer rises very quickly. Because air is not good at heat transfer, when there is no wind, the heat exchange between the upper and lower air is very small, which makes the vertical difference between cold and hot temperatures very significant, leading to the abnormal phenomenon that the density of the lower air is less than that of the upper air. In this case, if there is a tree in front of it and it grows in a relatively humid place, the light obliquely projected downward from the top of the tree will be refracted because it enters the air layer with high density. When the refracted light reaches the hot and thin air layer near the ground, total reflection occurs, and the light is reflected from the low-density air layer near the ground back to the higher-density air layer above. In this way, after a downward concave arc light, the image of the tree is sent to people's eyes and the reflection of the tree appears.

Because the reflection is below the real thing, it is also called a mirage. This kind of reflection can easily give people the illusion that there are trees by the water, thinking that there must be a lake in the distance. Most people who have traveled in the desert have had similar experiences. A photographer who filmed the film "Climbing Mount Everest in Hishapang" saw such a mirage while walking on a vast arid grassland. He ran in the direction of a mirage, trying to fetch water for cooking. When he ran there and saw that there was no water, he found himself cheated by a mirage. This is because hay, like sand, can be heated by the scorching sun, which gradually increases the density of the air layer from bottom to top, thus creating a mirage.

No matter what kind of mirage, it can only appear in windless or extremely weak weather conditions. When strong winds combine, which causes the agitation and mixing of the upper and lower air, the air density difference between the upper and lower air decreases, and there is no abnormal refraction and total reflection of light, then all illusions disappear immediately.

In a word, this is a very interesting refraction phenomenon. Respondents: 726600064 | Level 2 | 2010-1-19 20: 41.

Because light only travels in a straight line in a uniform medium, if the density of the medium is not uniform, light will not travel in a straight line, but will be refracted. Mirage is because the density of the atmosphere is not uniform, so that the light of objects can't enter our eyes, but some light that shoots into the air is refracted and enters the eyes of observation. Looking against the light, we feel that we have seen distant objects. Interviewee: One billion Why | Level 1 | 2010-1-2116: 50.

When light propagates in the air with uneven density distribution, it produces a mirage through reflection. In summer, the temperature in the lower layer of the sea surface is often lower than that in the upper layer, the density is higher than that in the upper layer, and the refractive index is also higher than that in the upper layer. We can think that the air on the sea surface is composed of a large number of water vapor layers with different refractive indexes. When the light from distant peaks, ships, buildings and people shoots into the air, it deviates from the normal direction more and more because of continuous refraction, and the incident angle of entering the high altitude will increase continuously, resulting in total reflection, and the light will reflect back to the ground. People can see the scenery hanging in the air in the distance by backlighting. Mirages can also be seen in the desert. When the sun shines on the sand, the hot air layer near the sand surface often has a lower density and a lower refractive index than the upper air. The light emitted from distant objects to the ground will be refracted when it enters the hot air layer with small refractive index, and the incident angle will gradually increase and total reflection will occur. People can see the reflection of distant objects against the reflected light, as if it were reflected from the water. Pedestrians in the desert are often confused by this sight, thinking that there is water ahead and rushing forward, but they are always in sight.

The simple answer is the refraction of light: tomato water | secondary | 2010-1-23 21:00.

These phenomena are real in our world.

In calm seas, rivers, lakes, snowfields, deserts or Gobi, occasionally towering towers, city walls and trees appear in the air or "underground", which is called a mirage. This illusion often appears on the sea surface of Penglai, China. The ancients attributed it to the dragon, exhaling and forming the tower wall, hence the name. Mirage is the result of light refraction in vertical gas layers with different densities. It is often divided into upward, downward and sideways mirage.

Let's do an experiment: take a cup, pour half a glass of water, put it in the sun, and then insert a chopstick into the cup. This is when you see that the chopsticks in the water are broken from those on the water. This is caused by light refraction; When light propagates in air with the same density, the speed of light is constant and always goes straight; However, when light obliquely enters water from the air, the density of water changes, the speed of light changes, and the direction of progress twists and turns.

A mirage in the desert is the refraction of sunlight when it meets air with different densities. In the desert, the sand is baked by the sun during the day, and the temperature on the surface of the sand layer rises rapidly.

Due to the poor heat transfer performance of air, when there is no wind, the vertical temperature difference over the desert is very significant, with high air density in the upper layer and low air density in the lower layer. When sunlight enters the low-density air layer from the high-density air layer, the speed of light changes, and after the refraction of light, the oasis in the distance appears in front of people.

On the sea or river, this kind of "mirage" phenomenon happens from time to time.

A mirage in the desert is far away from us. I don't know how long it will take if I just walk. Of course, the earth is round, and you can walk on your back, but the distance is longer. There are many kinds of mirage, which can be divided into upper, lower and side according to their position relative to the original. According to its symmetrical relationship with the original object, it can be divided into positive, lateral, positive and negative; According to the color, it can be divided into colored mirage and colorless mirage. Interviewee: Xia Mo Y Macchiato | Level 1 | 2010-1-23 21:26

The formation of a mirage

Mirages often appear in coastal areas and occasionally can be seen in the desert. People can see houses, people, mountains, forests and other scenery, which can be moved and lifelike. Some people think it is a fairyland on earth. Now people say that a mirage is the result of atmospheric refraction, which refracts distant scenery to the nearby. In fact, this is a self-defense that modern science cannot explain.

Within the three realms, there are also many layers of material space. The nine-story heaven and eighteen-story hell mentioned in religion, such as heaven and man, ghosts and gods, are all in different spaces. We human eyes can't see them.

The light that people in our space can see is in the visible range (400-700 nm). We see matter because our eyes can receive visible light reflected by matter. At night, we can't receive the infrared rays emitted by substances. Even in the visible range, if the light is too strong or too weak, we can't see it. The human eye is composed of the largest particles composed of the substances in our space and the largest molecules, and it is only suitable for seeing light within a certain energy range.

If it is a layer of space particles composed of molecules slightly smaller than the largest layer of particles, it is invisible to the human eye, let alone the space of smaller particles composed of molecules. For people, the light reflected by these substances is invisible light. However, the life in this space can receive the light reflected by the matter in this space and can see the matter in this space, because the molecular particles that make up their eyes are different from those of human eyes.

A mirage is the true embodiment of another space. Under the movement of matter, it is reflected in our space. A mirage happened at sea. The air humidity here is high, and the air humidity in a certain range is relatively high and the thickness is relatively large, which makes a large area of water vapor mistakenly form a huge lens system under the movement. Just like a huge magnifying glass and microscope, it reflects the scene of another space in the microscopic world to our space. The human eye can observe it.

In addition, the mirage people see is sometimes moving, and so are the substances in space. In the desert or other places, if the material can form a huge microscopic observation system under the movement, people can observe another space, which is what people call a mirage.

Mirages often occur after rain, when the air humidity is high and it is easy to form a lens system.

When the temperature near the ground changes sharply, it will cause a huge difference in atmospheric density, and the distant scenery will undergo abnormal refraction and total reflection when the light propagates, thus causing a mirage.

Penglai County, Shandong Province, China often sees the illusion of miaodao islands in the Bohai Sea, which is called a "mirage".

Mirage is the result that the temperature near the surface layer changes greatly, the air density changes strongly with the height, and the light is refracted to the observer's eyes in the vertical gas layer with different densities. It is often divided into upward, downward and sideways mirage.

In fact, what astronauts see in space travel is an enlarged view of the earth, which is sometimes called a mirage. Respondents: enthusiastic netizens | 2010-1-2919: 44.

In summer, on the calm sea, overlooking the distance, you can sometimes see mountains, ships, towers, pavilions, cities, temples and other scenes in the distance. The ancients didn't understand the scientific reason of this scene, and thought it was formed by the breath of dragons in the sea (that is, a mirage), so it was called a mirage, also known as a mirage.

In fact, when light propagates in air with uneven density distribution, it will be totally reflected and form a mirage. In summer, the lower air on the sea surface has lower temperature, higher density and higher refractive index than the upper air. We can regard the air on the sea surface as composed of many horizontal gas layers with different refractive indices. When the light emitted by distant peaks, ships, buildings and people shoots into the air, it deviates from the normal direction more and more because of continuous refraction, and the incident angle of entering the high altitude increases continuously, so that total reflection occurs and the light is reflected back to the ground. When people look against the light, they will see distant scenery hanging in the air, which is the so-called "mirage".

Mirages can also be seen in the desert. When the sun shines on the sand, the density of the hot air layer near the sand surface is low, and the refractive index is smaller than that of the upper air. The light from a distant object to the ground is refracted when it enters the hot air layer with a small refractive index, and the incident angle gradually increases, or total reflection occurs. When people look against the reflected light, they will see the reflection of distant objects, as if they were reflected from the water. Pedestrians in the desert are often confused by this sight, thinking that there is water ahead and rushing forward, but it is always beyond their reach. ?

In hot summer, the above phenomenon can sometimes be seen on the asphalt road. The air layer near the hot road surface, like the air layer near the hot sand surface, has a smaller refractive index than the upper air. Light emitted from distant objects to the road surface may also be totally reflected. From a distance, the road surface looks particularly smooth, just like being drenched by water. Respondents: Dependent on Bad Kids | Level 1 | 2010-1-29 20: 25

A mirage is a natural phenomenon formed by light refraction. In a calm sea, river, lake, snowfield, desert or Gobi, sometimes there are towers, city walls and trees in the air or "underground", which is called a mirage. This illusion often appears on the sea surface of Penglai, China. The ancients attributed it to the dragon, exhaling and forming the tower wall, hence the name. Mirages often appear on the sea and in the desert. Mirage is the result of light refraction along a straight line in gas layers with different densities. There are many kinds of mirage, which can be divided into Shanghai mirage, Xiahai mirage and seaside mirage according to their position relative to the original objects. According to its symmetrical relationship with the original object, it can be divided into positive, lateral, positive and negative; According to the color, it can be divided into colored mirage and colorless mirage. Respondents: 00cderfv | Level II | 20 10- 1 1.