As a product of the electric-vehicle era, the flashlight has undergone hundreds of years of updates and iterations since its birth. The birth of the flashlight greatly facilitates human life and gives us more guarantees for travel at night. A small flashlight . Just a light press can form a huge light column, just like laser rod .
I believe many people did one thing when they were young, , that is, use a flashlight to shine the sky, and see that beam of light hit the dark sky, maybe you can imagine whether the beam of light can reach space?
Theoretically, rays can spread infinitely, but when we turn off the flashlight, we can't see any traces left by the light. can't help but make many people ask questions. Open flashlight and close it immediately. Will the light disappear directly or continue to spread?
What is light
The essence of light is a photon stream in a specific frequency band, which comes from the mutual excitation of the electric field and the magnetic field. The excited energy promotes the high-speed motion of the photons.
light emission first requires a light source. In the light source, atoms and molecules in the light source produce light radiation . This radiation extends infinitely from the outside like countless rays, and can shine its own light on other objects. forms a light source with different lights according to the size of the light source and the intensity of the light radiation.
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Some planets in the universe can glow. We call this kind of planet a star, and the star closest to the earth is the sun. The sun emits light and releases a lot of heat energy. Sun light The existence of the earth is an important condition for the birth of life. Some people may ask when looking at the bright moon, is the moon a star? Although in our opinion, the moon can emit light, it is not the light formed by the moon itself, but the reflection of the sun's light.
Light plays a crucial role in humans and even the entire nature. The role of light is not just lighting. The growth of any green plant cannot be separated from Photosynthesis . There are also many elements in the human body that need to be synthesized under light. It can be said that light is the cradle of life.
In the future, with the lack of various non-renewable resources, the energy carried by the sunlight will be an important energy for human beings. The emergence of artificial light source also makes the night no longer afraid. As long as there is a place where human civilizations gather, even when it comes to darkness, the lights are still bright and bright. It can be said that both natural light and natural light have changed people's lives and benefited people's lives.
Research history of light
Light is a magical substance. We can see light illuminating an object, but when we touch it, it is like air. In order to understand the existence of light , humans have never stopped exploring light. Regarding the study of light, we can even trace back to the ancient Greek and the Spring and Autumn Period and the Warring States Period more than 2,000 years ago.
In the Spring and Autumn Period and the Warring States Period, Mozi , the founder of , Mozi , passed the experiment of , the world's first small hole imaging , and recorded relevant knowledge about light in " Mo Jing ", explaining the propagation of light, and the movement of light along a straight line. European Euclidean also wrote the book "Optics" , and used mathematical laws to prove the reflection of light .
"Small hole imaging"
Mozi and Eucli It is just a study of some basic properties of light. As the theory becomes more and more mature, scientists began to study the essence of light, and analyzing what light is from a physical perspective has become the research topic. Human beings have experienced a long time to understand the essence of light, but there has never been a truly convincing theory.
It was not until the seventeenth century that two relatively convincing theories of
Descartesian uses " ether " hypothesis to illustrate the nature of light . It believes that the color of light originates from the different rotation speeds of ether particles, emphasizing the influence of media , and can be said to be the founder of the fluctuation theory. Hu Ke compared light waves with water waves to prove the fluctuation of light. made the diamond shine by rubbing it, proving that light is actually a kind of vibration.
ether hypothesis: The earth travels through the medium carrying light, ether
particle theory main praise is Newton . Newton proposed the particle theory of light through the dispersion of light, and also discovered various colors of light through the dispersion experiment of prism . Newton explained the refraction, diffraction and interference of light through further research, and improved the particle theory. The microparticle theory has become increasingly recognized and almost dominated. Nevertheless, Newton was not all correct, and some theories proposed by Newton at that time were later proved to be wrong.
In the 19th century, some studies have found that some of Newton's views have proved the errors of some Newton's views, and the fluctuation theory has gradually become mainstream again. Finally in the 20th century, Einstein proposed the quantum of light, saying that Compton confirmed the particle nature of light, and the combination of the two made people realize the wave-particle duality of light.
The fluctuation of light
In addition to the particle theory and the fluctuation theory, In the 19th century, Maxwell discovered through calculations that the speed of light is the same as that of electromagnetic wave . Later, the existence of German physicist Hertz . Marconi discovered multiple electromagnetic waves based on the theory of the two after multiple experiments. also proved that light is an electromagnetic wave . Compared with other electromagnetic waves, light is essentially the same, but there are great differences in wavelength and frequency.
Light itself is a magical substance, its essence is covered with layers of mystery, Scientists of all ages search for the truth layer by layer like stripping silk and cocoon, and future generations stepped on the shoulders of their predecessors to continue moving forward. In modern times, our understanding of light has become more profound and comprehensive.
Overall, humans' understanding of The essence of light is still mainly based on the fluctuation theory and the particle theory. At a certain historical stage, with the breakthroughs in related research, the two theories of have advantages with each other, but overall, the research direction is moving forward.
The motion state of light
In primary school mathematics textbooks, we will understand the lines of . Lines can be divided into straight lines, rays and line segments . From this property, light is actually a ray. Theoretically speaking, after light is emitted from the light source, it can propagate infinitely to the surroundings, but the light we often see has a limited range, which is actually related to the motion state of the light.
Ink Zi discovered the linear propagation of light through small hole imaging experiments. Newton believed that light is the particle stream , and used this to further analyze the linear propagation of light. It is believed that Because the light source emits particles outward, a linear motion is made in the vacuum or uniform substance due to inertia. is precisely because of this, we can see that in life, light will not turn.
The movement of light propagates around in the form of electromagnetic waves, and the speed of electromagnetic waves is very fast, so when we turn on the flashlight, it will become bright in an instant. When we cut off the power supply, the electrons and magnetic fields will stop working and the light will disappear.
Some people think that sunlight can be transmitted to the earth, so the light from the flashlight should also be able to travel far, but in fact it is not. First of all, the reason why we can see sunlight on the earth is that the light particles emitted by the sun pass through the atmosphere at the speed of light and finally come to the surface of the earth.
The sun is so far away from the earth that it takes sunlight to reach Earth also takes eight minutes . Relying on the continuous output of the sun and the powerful energy contained in the sunlight, the sunlight can finally come to the earth. Being on the earth, after filtering by the universe and the atmosphere, we can only feel the soft sunlight, but in fact the sun has powerful energy. If there is no atmosphere, the entire earth will be like on an oven. When the sunlight shines on the earth, these energy is constantly consumed, and finally supports the sunlight to come to the earth.
Although our flashlight can emit light, the energy contained in this light is extremely weak and is not enough to support the spread of flashlight over long distances. When the flashlight is turned on, the energy of the particles in the air will be gradually consumed during the forward transmission process, so the final range is limited.
The reason why we can see a light column when we open flashlight is because the flashlight is constantly emitting light, supporting the continuation of the light column. However, due to insufficient energy, this light column can only be maintained within a certain range. Once we turn off the flashlight, without the support of energy, the light will disappear. So when we turn on the flashlight and turn it off immediately, Even if the light in the air will spread, the distance from the outgoing is very small, which is equivalent to disappearing directly.
The effect of light
Although the movement of light is in a straight line, it is often refracted due to various media during the movement. What we call mirage is a natural phenomenon formed by refraction and reflection of light. artificial light is actually no different from sunlight in terms of speed, but because the energy contained in the flashlight is too weak, it is difficult for the flashlight to obtain good penetration power, and it is often consumed shortly after it is shot out.
The energy of light is reflected in many aspects during movement. The most straightforward thing is reflected in heat. The more energy the light contains, the hotter it is often. For example, in summer, because of the earth's revolution , the northern hemisphere is closer to the sun. The distance from sunlight to the earth becomes shorter, energy consumption decreases, so the climate becomes hotter and plants grow faster. The same is true for artificial light. Now some flashlights are very bright and very far after they are turned on, but this kind of flashlight often becomes hot after working for a period of time.
In fact, theoretically speaking, as long as the energy of is strong enough, flashlight can also spread for a long distance. once had a plot in Ultraman movies. Because of the disappearance of the sun, scientists developed an artificial sun . This sun shines on the entire planet and can be seen even in the universe. With the development of technology, perhaps we can also invent flashlights that can shine into space in the future.
In fact, from the satellite photos, we see that when night falls, many small light spots will appear on the earth, but once the power is out, it will disappear. This also proves that the propagation of light requires energy supply. After the energy supply is lost, even if the light in can spread, it will also be exhausted and disappear.
We observe the universe through giant telescope , which is also inseparable from light. In addition to the sun, there are many stars in the universe. Their light finally emanates to the direction of the earth through refraction and reflection. After we accept it, we can restore the scene from a certain moment and a certain place. Light is magical, not just lighting, it often contains various information.
The use of light
Light is crucial to humans. Many people may not understand light, but the use of light is very wide. has a wide range of applications in energy, electronics, and communications. Because of the study of light, we discovered the color of light, which allowed us to see color TV . Because of the study of light imaging, we found a method for to treat myopia . Let us use light energy indoors to plant vegetables in , so that we can eat off-season vegetables.
Light energy is also an important clean energy and can be used for power generation, etc. will be further widely used in the future. It can be said that the research on light energy has greatly promoted the progress of mankind.
Human beings have never stopped their pace in the study of light. Some people have put forward a guess. If moves more than , the speed of light can be studied, and we still don’t know about this, but with the development of technology, time will eventually tell us the answer.
