Why is there no shadow of a lamp on the lamppost reflected by the river at night?

In fact, there are shadows, mainly because the umbra and penumbra of the shadow are superimposed on each other, making the shadow blurred. The principle is the same as the "shadowless lamp" in the operating room of a hospital.

Let's quote the "shadowless lamp principle" to explain:

Due to the straight line propagation of light, when light hits an opaque object, a shadow is formed behind the object. Shadows vary from place to place and at different times. For example, the shadow of the same person in the sun is long in the morning and evening, and short in the noon. �

By looking at it, we can see that the shadow of the object under the electric light is particularly dark in the middle and slightly lighter on the periphery. The darker part of the shadow is called the umbra, and the darker part of the shadow is called the penumbra. The occurrence of these phenomena is closely related to the principle of linear propagation of light.

The following experiment will reveal the mystery. �

We place an opaque cup on a horizontal table top and light a candle next to it, and a clear shadow is cast behind the cup. If two candles are lit next to the cup, two shadows will be formed that overlap but do not coincide, and the overlapping parts of the two shadows are completely black, and therefore completely black. The place where there is only one candle next to the umbra is the half-light and half-dark penumbra. If you light three or even four or more candles, the umbra will gradually shrink and the penumbra will appear many levels and gradually become darker.

The same is true for objects that can produce shadows composed of umbra and penumbra under electric light. Electric lamps emit light from a curved filament, and the light emitting point is not limited to one point. Light coming from one point obscures the object, while light coming from another point is not necessarily blocked.

Obviously, the larger the area of the luminaries, the smaller the umbra. If we light a circle of candles around the said cup, the umbra disappears and the penumbra is too faint to be seen. �

For this reason, the ceiling light in the operating room is composed of several lamps with great luminous intensity arranged in a circle on the lamp plate to form a large-area light source. In this way, the light can be irradiated onto the operating table from different angles, which not only ensures that the surgical field of view is sufficiently bright, but also does not produce obvious umbra and affect the operation. Hence the name "Shadowless Lamp".

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In fact, there is a shadow because the light of the lamp tube of the lamppost by the river is soft, the light source area is large, the illumination angle is relatively more, and the light is not concentrated, so the shadow is not obvious, while the light of the bulb is strong and the direction is concentrated, and the shadow is obvious.

If the house light is directly underneath, then a dark shadow will form at your feet. If it's between two lights, then it's going to be two shadows.

Lonely and lonely, only his own shadow is with him. Alone. This is the imagery of literature. Why shadows form is a matter of physics ...

Shadows are because light travels in a straight line, and objects block it, which naturally leaves shadows.

In fact, there are shadows, the light of the tube is soft, the light source area is large, the illumination angle is relatively more, the light is not concentrated, so the shadow is not obvious, and the light of the bulb is strong and the direction is concentrated, and the shadow is obvious.

Is it similar to the shadowless lamp in a hospital? You bundle a hundred light bulbs together, and there is no shadow!

The water surface is equivalent to a plane mirror, and the lamp is imaged through the water surface, because there are always water waves on the river surface, like many plane mirrors with different orientations, the electric lamp can be imaged in each plane mirror, so it is not a lamp, but a pillar of light

Answer: This is because there are always water waves on the surface of the river, like many plane mirrors with different orientations, and the electric lamp can be imaged in each plane mirror, but the position of each image is different, and these images are combined to form a pillar of light

It is the reflection of light from the water, because the water surface is not flat, and the water fluctuates, so the water in the whole line has some light that can reflect the light to your eyes, so what you see is a pillar of light.

It is very simple, because the electric lamp is radiating in all directions, when the human eye looks against the light, due to the difference in the spatial orientation of the water surface and the fluctuation of the water surface, diffuse reflection and total reflection will occur, and then through a series of reflections into the human eye, so as to see a pillar of light.

Under the street lamp, even directly under the street lamp, there will be irregular black shadows around the soles of the feet, that is, shadows. And there will definitely be a protruding part in front of the shadow, which is the shadow of the head. As long as there is light, there must be shadows.

Brother, I don't know what you're seeing, but I'm too tired from work to have fantasies...

Because his body blocked the shadows.

Street lamp, the street lamp is on the pole, generally, another long pole is hung on the top of the street lamp, and then the lamp, then, the two people are standing directly below the lamp, then there is no shadow. Just like the sun is in the sky, the sun is basically (not all) above you and your shadow is very short, and in the afternoon, your shadow is very long. And that pole is right below the lamp, so there's a shadow, don't believe it, you're going to give it a try.

When your gaze forms a specific angle with the light, the shadow will condense into a single point, which is what you call shadowless.

They stand directly under the street lamp, and only cast shadows under their feet, where the light would not have reached.

This is normal. If you have time to look more, you will naturally find out why.

The shadow is getting shorter and shorter, because with the lengthening of time, the temperature of the tungsten wire is getting higher and higher, so that the resistance value also changes a little, and then the brightness intensity also changes a chain. So the shadow will get shorter and shorter!!

Light travels in a straight line, creating shadows where it can't be illuminated, and there are rays at all angles due to the number of light sources, so there are no shadows.

The sun is a light source, but it is regarded as a point light source because it is far away. The principle of shadow formation is known. When the light is blocked, it is a shadow.

Under light, perhaps due to multiple light sources. Or multiple light sources formed by one light source. For example, a mirror forms a light source.

Actually, I don't know what you mean by repetition. If the edges of the finger shadow are blurred, it is due to the diffraction of light. You can read the physics book for the third year of high school.

Sunlight is almost parallel (almost non-overlapping), there are many light sources, light is not parallel, of course there are many.

There are as many shadows as there are light sources, but some are generally invisible.

The sun is a source of light, and there are many lights on the road, i.e., there are many light sources. So there are many shadows.