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Anonymous users2024-02-081 Ask a question:
What do you see when you observe the phenomenon of sunlight passing through the shade of trees? What questions can be asked?
See a lot of circular spots, where does this spot come from? I also saw some non-circular spots, how did these spots form? )
2 Make conjectures and **:
It may be that the hole that meets the light is approximately circular, so that the edge of the shadow is approximately circular, and if the aperture that transmits light is non-circular, then the light spot formed is also non-circular;
It may be that the sun is too far ahead to form a spot (image) The size of the hole may affect the shape of the spot.
Which conjecture is correct?
3. Gather factual evidence.
Students work in groups of 2-3 and observe the image of sunlight passing through small holes in the paper on the screen.
The image is made by letting sunlight pass through various small holes of different shapes (triangles, squares, diamonds, trapezoids, etc.) on the piece of paper.
The image is formed by letting sunlight look through various large holes of different shapes (triangles, squares, diamonds, trapezoids, etc.) on the paper.
4 Draw conclusions and explanations.
By analyzing the collected facts, it can be concluded that the image formed by the small hole is circular, independent of the shape of the hole, and when the hole is large to a certain extent, the circle disappears, and a spot similar to the shape of the hole is obtained.
The principle of direct advance of light can explain the above conclusion: that is, a luminous point on the surface of the sun forms a spot on the screen through a small hole, and all the luminous points form a spot corresponding to themselves, thus combining into an image of the sun.
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Anonymous users2024-02-07Think of the process as pressing the block to the level (this process the block goes down and the water rises) and the process of going from completely submerging in the water to pressing it to the bottom of the container (the position change is also the wood falling and the water rising) (to be able to see the container so that the water does not overflow to the outside and the water can overflow is also very simple). ）
In the above two processes, the potential energy changes of the water and the wood block are calculated, and the work is calculated.
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Anonymous users2024-02-06According to the principle of small hole imaging, the spot in the shade of the tree should be a small sun, and during a partial solar eclipse, the spot seems to be missing. In fact, the sky is bright during the day, and there is no clear boundary between the spots under the shade of the trees, so during a partial solar eclipse, there is no precise boundary line on whether the spot is a place with a dark brightness, so it looks round.
This is not only the case during partial solar eclipses. Because the solar light source is not a point, but a large sphere, a surface light source will image a small hole. The round shape is the shape of the sun.
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Anonymous users2024-02-05The shape of the light spot in the shade is mainly related to the following factors:
1.The shape and arrangement of leaves
The shape and arrangement of the leaves affects the occlusion and passage of light. Leaves of different shapes and closely arranged are more likely to block sunlight and may form smaller and more dispersed light spots; Regular-shaped, sparsely arranged leaves may allow light to penetrate more intensively, resulting in a larger, more concentrated light spot.
2.The angle of the light source
The light source is the position of the sun in the sky, and the angle of the light source affects the angle at which the light penetrates the leaves, thus changing the shape and distribution of the light spot. For example, when the sun is at the zenith, the rays come down vertically, forming a rounder spot; As the sun approaches the horizon, the rays of light fall at an oblique angle, forming a spot that may be elongated and elliptical in shape.
3.Environmental conditions
Environmental conditions such as wind and direction can also have an impact on the foliage, changing its arrangement and thus the shape of the spot. For example, strong winds may cause the leaves to swing, causing a change in the shape of the light spots.
The light spots under the shade of the tree are the real image of the sun, but because the gaps between the leaves of the tree are large and small, the real image of the sun is different, and the small gap (equivalent to the small hole envy stool) becomes the real image of the shape of the real sun, and the gap becomes the shape of the gap. In general, the shape of the spot is the result of light passing through the leaves and projecting onto the ground, which is influenced by a variety of factors such as the shape of the leaves, their arrangement, the angle of the light source, and environmental conditions.
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Anonymous users2024-02-04It is caused by imaging of the small hole. Because the sun is round, the spot on the ground is also round, and the spot of the circle is formed by the round sun. The shadow is the place where the light does not hit, and the spot is the place where the light hits, the circle under the shade of the tree is the spot of light and not the shadow, and all the circular spots on the ground are a standard circle, only the shape of the sun matches it.
Aperture imaging is a physical phenomenon that occurs when light travels in a straight line. With this phenomenon, it can be proved that light travels in a straight line in the same homogeneous medium.
About 2,450 years ago, Li Jian, a scholar in China, sent Mo Zhai (Mozi) and his students to do the world's first experiment on the inverted image of the aperture, explaining the reason why the aperture was inverted, and pointing out the nature of the straight line progression of light. This is the first scientific explanation of the linear propagation of light.
If a plate with a small hole is used to block between the wall and the object, the reflection of the object will be formed on the wall, and we call this phenomenon the image of the hole. Moving the middle plate back and forth will also change the size of the image on the wall, which illustrates the nature of light propagation along a straight line, and the size of the image in the image of the small hole is related to three factors:
1. When the object distance and image distance (that is, the length of the camera obscura) are constant, it is related to the size of the object itself: the larger the object, the larger the image;
2. When the size of the object itself and the length of the light screen (the length of the camera obscura) are constant, it is related to the object distance: the larger the object distance, the larger the image;
3. When the distance between the object and the size of the object are changed violently, it is related to the distance of the light screen (dark box): the farther the light screen, the larger the image.
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