How is the spectrum proved step by step?

The measurement of the speed of light is a great development of technology, but the most important technology is not the study of the speed of light, but the study of the color of light.

Newton observed the characteristics of light through a prism. When he is equipped with an experimental device, he will produce a spectrum on the screen behind the prism, which is a rainbow. The so-called "red shift" and "blue shift" are based on spectral position.

Newton found that white light is impure, and white light is the most impure light. White light can be divided into polychromatic colors, and polychromatic colors can be combined into white light.

Joseph Flawn Hof (1787~ 1826) is a mirror grinder and glassmaker in Munich. He once designed a precision grinder, and he also improved the telescope. He is very familiar with the properties of various glasses and knows how to process them into high-quality optical instruments.

Flawn Hof compared the light refraction of various glasses and let sunlight pass through a prism made of a single glass, but he found that because the colors of the spectrum were concentrated in a small range, it was impossible to make an accurate comparison at first. Therefore, Flawn Hof drew up a plan to further expand the spectrum.

Thus, the Flawn Hough Line was born.

The colors of the solar spectrum are not seamless and continuous. What we see from the spectrum is the irregular distribution of narrow spectral lines. This is the Flawn Hof line.

Flawn Hof believes that "these spectral lines prove that the components of decomposed white sunlight are not composed of continuous spectra with different refractive powers, and the light comes from a certain color scale, so the dark lines are gaps in the spectrum, and these gaps correspond to the lack of light. If this spectrum is generated by sunlight passing through a prism made of the same material every time, then these spectral lines will always be in the same part of the spectrum, with the same order and position, the same density and brightness. If the materials are different, the quantity, order and brightness have not changed, but the mutual distance between spectral lines is different. "

People always think that the light emitted by the sun and other stars is the same, but Flawn Hofer found that the spectrum of stars is different from that of the sun.

This led to an important research, namely spectral analysis. Spectral analysis is an important scientific achievement in19th century. Because of spectral analysis, chemists can point out the situation of tiny elements, and astronomers have begun to move towards astrophysics. As for metallurgy, engineering and other aspects, trace substances can also be accurately determined to determine quality and accidents.

At that time, people used the relationship between elements, atoms and light, but why did they keep emitting light with different colors? /kloc-people in the 0 th and 9 th centuries don't know that this is the category of atomic physics.

The "bunsen burner" in the laboratory today is a technical tool invented by scientist bunsen burner, and it is a gas lamp with sufficient gas source. Because this kind of flame has sufficient air supply, it has almost no color and high heat, which is very helpful to observe the color.

German chemist Benson (181~1899) and his colleague Schhoff (1824~ 1887) used this lamp to study the combustion and luminescence of many elements.

They use platinum wires to slowly bring all kinds of salt close to the flame, and they can observe the spectrum of steam combustion on the salt. "These phenomena in front of us belong to the most brilliant artificial optical phenomena. Now we only see the spectrum corresponding to the burning salt, which appears with the greatest luster. In previous experiments, the biggest feature of the spectrum was blurred by alcohol light. "

Bunsen and Kirchhoff concluded that metal has its special flame reaction. In order to further cause the flame reaction of refractory metal compounds, the two of them also used electric spark because it provided strong light.

The spectrum of incandescent solid is continuous. Since the spectrum of an element has nothing to do with the compounds it contains, a good way to test an element is flame reaction. In the test, the spectra of various elements in the compound will not interfere or affect each other. But the most important thing is that the verification method provided by Bunsen and Schhoff shows great sensitivity. Benson described that in one experiment, one milligram of 3 million sodium was enough to obtain a clear spectrum.

Using spectral analysis, people quickly found some chemical elements that were neglected in the study because they only appeared in a small distribution range. Like rubidium and cesium, it was discovered by Bunsen through flame color. Later, through the spectrum, the existence of indium, gallium and scandium was discovered. The composition of unknown compounds can also be determined by spectral analysis.

Fraunhofer has observed in laboratory experiments that the two dark lines of the solar spectrum are just in the position of the bright lines of the sodium spectrum. Leon Foucault, Bunsen and Dick Shikhov explained that if bright light falls on less bright sodium vapor, there will be "sodium line inversion". In the spectrum, the original bright line is darker than the rest. Using the corresponding experimental methods, the spectral lines of other chemical elements also have the same situation.

What is the reason?

Luminous gases and vapors absorb the colors they emit. In addition to the emission spectrum caused by the light of the luminous body, there is also the absorption spectrum. When light passes through luminescent gas and steam, an absorption spectrum is generated. At this time, the absorption spectrum is the "opposite" of the emission spectrum to some extent. When there is no absorption, the position of dark lines belonging to elements in the absorption spectrum is exactly the position of bright lines in the emission spectrum.

This understanding explains the formation of Fraunhofer lines in the solar spectrum.

Shhoff wrote: "In order to explain the dark lines of the solar spectrum, it must be admitted that the sun's atmosphere surrounds the luminophore, and the luminophore itself only produces a spectrum without dark lines. People can assume that the sun is a solid or liquid high-temperature core surrounded by a slightly lower temperature atmosphere. "

Elements in the sun's atmosphere absorb their own light, thus forming dark lines. In fact, further measurement and comparison show that many elements on the earth are hot steam in the solar atmosphere. As long as we expand the research on the spectrum of stars, we will find that the elements on the earth also exist in stars.

In the history of chemistry, an element was first discovered on the sun.

At that time, people already knew how to place and dim the telescope with a spectrometer to obtain the spectrum of the hot gas layer around the sun, not the spectrum of the sun itself. Therefore, the spectrometer shows not the absorption spectrum but the emission spectrum. Under normal circumstances, the dark Fraunhofer line appears bright. British astronomer and physicist Joseph Norman Locar observed a bright yellow line here, which belongs to an unknown element. Locar guessed that there was an unknown element on the earth, and he named it helium. Helium on the earth was discovered in 1895 for almost 30 years, and there are traces of helium in some minerals. New elements were first discovered in the sun and later found on the earth, which is convincing evidence that the same elements also exist in celestial bodies.

Since then, spectral analysis has made great achievements in astronomy and astrophysics.

People can infer the surface atmospheric temperature from the spectrum of the star, and then get the main points of the temperature of the star itself.

The spectrum of the light source is slightly deviated and can only be measured by the most precise means. The deviation depends on the moving speed of the light source towards us or away from us. According to this, the velocity of stars can be measured by spectral analysis.

/kloc-the rapid development of photography technology in the 0 th and 9 th centuries promoted spectral analysis.

At present, spectral analysis has changed from visible light to invisible light, which can determine the chemical composition of distant planets and prove the universality of chemical elements.