Why is the shadow short in time Why is the figure short in time

1. First of all, you need to understand what the concept of shadow is

The light that travels in a straight line is blocked by the shading object, thus creating a shadow on the back of the object. Light can pass through transparent objects, so translucent objects do not form shadows. Depending on the angle of light, the shape of the shadow is different.

The shadowless lamp that we often say in medicine is formed by using a group of multiple lamps to shine from all angles to dilute the shadow of the object"No shadow"effect, in fact, there is a shadow. I think that only objects that can allow light to pass through completely can not form shadows.

2. Explain the question you asked.

Because the rotation and revolution of the earth cause the position of the sun to hit the earth to change, so the position of the sun changes, and of course the position of the shadow also changes The key to this problem is: the angle of the sun's altitude changes every moment, and the angle of the natural shadow will change, so the duration of the human shadow can be easily understood.

Optical Problems!! The different angle of light is the main reason for the length of the shadow, such as the light source is above the head at noon, and the angle of light is 90 degrees, the shadow is the shortest at this time, and the light is tilted to 10-30 degrees in the early morning and evening, and the shadow is longer than the figure at noon.

Light travels in a straight line! When the angle of incidence of light is different, then his projection is also different! The length of the figure changes with the angle of the incident light! Answering your question in this way should make sense!

It has to do with the sun ...

At twelve o'clock in the middle of the day, the sun should be the shortest figure.

The figure of the upper and lower afternoon is the longest.

It has to do with the angle at which the light source emits light.

That's the difference between art and life.

It was taken from multiple angles by several machines, and then put them together, fool.

Lailai Overlord Golden Pill can permanently grow two centimeters and permanently extend for 20 minutes.

That's just acting, so why take it too seriously.

Mornings are longer.

Because in the morning when the sun is just over the horizon, the angle with the people is greater, and it is obliquely shining, and the shadow will be very long;

And at noon, when the sun rises to the middle of the sky, it is right above the person's head, and the angle formed with the person is very small, and the shadow is very short.

Here's why:

Because light moves forward in a straight line, when light encounters an opaque object, part of the light will be absorbed by the object, and part of the light will be reflected, while other light that is not blocked by the object will continue to move forward, and the phenomenon of shadows is called shadow.

So, if there is no light, how can there be a shadow? So, at night, when a person walks under a street lamp, the shadow becomes shorter and then longer, just as the shadow grows in the morning and the shadow is short at noon.

There are two types of shadows: umbra and penumbra

If you look closely at the shadows under the electric light, you will also notice that the shadows are particularly dark in the middle and slightly lighter around them. The particularly dark part in the middle of the shadow is called the umbra, and the dark part around it is called the penumbra. The occurrence of these phenomena is closely related to the linear propagation of light.

If you place a cylindrical tea tube on the table and light a candle next to it, the tea tube will cast a clear shadow. If two candles are lit next to the tea tube, two shadows will be formed that overlap but do not coincide. The part where the two shadows overlap is completely black, and this is the umbra; 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 candles, the umbra will gradually shrink and the penumbra will appear in many layers. The same is true for objects that can produce shadows composed of umbra and penumbra under electric light. The lamp is made up of a curved filament that emits light, not just one point.

Light from one point obscures the object, and light from other points is not necessarily blocked. Obviously, the larger the area of the luminous object, the smaller the umbra. If we light a circle of candles around the above-mentioned tea tube, the umbra disappears completely, and the penumbra is too faint to be seen.

According to the above principle, scientists have made a shadowless lamp for surgery.

It arranges the lamps with great luminous intensity into a circle on the lamp panel to form a large area of light source. In this way, the light can be irradiated to the operating table from different angles, which not only ensures that the surgical field of vision has sufficient brightness, but also does not produce obvious umbra, so it is named shadowless lamp.

Two conclusions.

1. Because light travels in a straight line in the same homogeneous medium.

As you walk towards the light, the light that you block becomes more and more concentrated, so it gets shorter.

After you pass the street lights, the light can shine through the area around you (in terms of flat surface.

Note: Generally, the degree from the center of the lamp part of the street lamp to the angle on both sides is 120 degrees, that is, there are 30 degrees left on each side, because no one will go there, and even if the light can reach the ground, it is too dark.

2. The reason for the formation of shadows is because light travels in a straight line. When it encounters an opaque object and is blocked, the dark area that forms is the shadow. When you walk under a street lamp and cast it directly on people, the dark areas (shadows) will become less (shorter) because the light travels in a straight line in the same homogeneous medium.

As you walk towards the light, the light that you block becomes more and more concentrated, so it gets shorter.

After you pass the street lights, the light can shine through the area around you (in terms of flat surface.

Note: Generally, the degree from the center of the lamp part of the street lamp to the angle of both sides is 120 degrees, that is, there are 30 degrees left on each side, because no one will go there, and even if the light there can reach the ground, it will be too dark, and the light source and the object will be connected, and the shadow must be connected into a line. When the head and feet, the light source is connected into a line, and the shadows of the head and feet are also together, so it is short.

Other times, it's a little longer and longer.

The reason why shadows are formed is because light travels in straight lines. When it encounters an opaque object and is blocked, the dark area that forms is the shadow. When you walk under the street lamp and the time is directed at the person, the dark area (shadow) will become less (shorter) and longer after walking.

Hello, our country is in the northern hemisphere, so standing in the sun in the morning and noon, the shadow still has a noticeable change. The most noticeable change is that the shadow grows in the morning because the sun is on the horizon.

By noon, the sun was overhead, so the shadows were much shorter. This is also a day of debate between the two children.

, however, in the current physics view, it is the level of pediatrics. If a person is at the equator, the shadow is getting shorter and shorter from morning to noon, so the reference.

The choice is very important.

At noon, the shadow of a person should be short.

When people are far away, the angle between people and lights is small, and the shadows formed are longer;

When people gradually approach the street lamp, the angle between the person and the light will become larger, and the shadow formed at this time will become shorter;

When a person passes by a street lamp and gradually moves away, the angle between the person and the light will become smaller again, and the shadow formed will become longer again Therefore, when a person passes by the street lamp, the shadow first becomes shorter and then longer

Therefore, choose D