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Bunsen and his lamp.
Bunsen was a German, and in 1830, he graduated from university at the age of 19. Later, in addition to teaching at the university, he also studied the gases coming out of the roof of the blast furnace and developed the method of gas analysis. In 1854, a gas factory was opened in the city of Hamburg, and Bunsen's laboratory was filled with gas.
Bunsen invented a new type of gas lamp that could easily adjust the size and temperature of the flame. This kind of lamp is still used in chemical laboratories today, and everyone calls it Bunsen burner.
The story begins with Bunsen's lamp.
When the Bunsen burner burns at its best, the temperature can reach 2300 degrees Celsius, and the flame is almost colorless. Sometimes the lamp is not properly adjusted, and the flame will shrink into the tube, and the copper tube will burn red, and the flame will turn blue-green. And when the glass tube is bent on the lamp, the glass tube burns red, and the flame turns yellow again.
These phenomena caught Bunsen's attention. He began to study how the color of the flame changes when various substances are burned on the lamp.
Bunsen took a grain of ordinary table salt with platinum tweezers and burned it in a flame, which immediately turned bright yellow, and at the same time smelled the choking smell of chlorine—the salt (sodium chloride) was broken down by the high temperature. But why did the flame turn yellow? Is it the role of chlorine or sodium?
In order to understand this problem, Bunsen selected some compounds that do not contain chlorine but contain sodium, such as soda ash (sodium carbonate) and miscanthus (sodium sulfate) for testing. If these substances can also turn the flame yellow, it is proof that sodium is at work.
And that's exactly what it turned out to be. As soon as the soda ash and miscanthus were put into the flame, the flame immediately turned yellow.
Finally, Bunsen burned the sodium metal in a flame, and the flame immediately turned bright yellow. This decisive experiment confirmed that it was indeed sodium that turned the flame yellow.
The success of the experiment led Bunsen to a new idea: could metals other than sodium also change the color of flames? He tested all the chemicals and metals in the lab.
Bunsen found that various compounds of potassium and potassium make the flame purple, while barium is a green flame, calcium is a brick-red flame, strontium is a bright red flame, and so on.
This was in the autumn of 1858, and he recorded these discoveries in detail in the notebook of his experiments.
Bunsen was so happy that he believed he had invented a new method of chemical analysis. This method does not require complicated equipment, and the operation is very simple, just put the substance to be analyzed on the lamp and burn it, and look at the color of the flame to know what metal it contains. What is needed now is to study the language of flame and understand what elements the various colored signals represent.
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Now there are many special lights for students on the market, and ** is not low, do we need to buy them? Can't fluorescent and fluorescent lamps be used? Faced with these problems, we learned the following:
There are many types of lamps and lanterns, which can be divided into incandescent lamps and cold light lamps from the perspective of daily use. The working principle of incandescent lamps is relatively simple, which is to heat the filament to an extremely high temperature and enter an incandescent state, so as to convert electrical energy into light energy and emit visible light. The main feature of this type of luminaire is that the temperature of the luminaire itself is very high, and the "color temperature" of the light emitting is low.
What is "color temperature"? Let's give you a simple example: suppose there is a piece of coal, burn it, then it will emit different light at different combustion temperatures, at lower temperatures, the color is reddish, and with the increase of temperature, the color changes to blue, which is the corresponding coloring temperature.
Color temperature only causes the color change of the object, for example, when choosing clothes in the shopping mall, experienced customers always take the window to see the color, and do not judge under the lights of the shopping mall, which is the reason, it can be seen that incandescent lamps will not affect people's eyesight.
The luminous principle of cold light lamps is more complex, and the bulb or tube of this type of lamp always has a phosphor inner coating. It also has a filament, but it does not work only by a red-hot filament, and the temperature of the lamp itself is not high, but the color temperature is often high, giving people the feeling of blue light, but it still has nothing to do with human eyesight.
From the above, we can know that as long as there is a correct and hygienic eye habit and sufficient illumination, it is enough to prevent myopia. If you don't have the right eye habits, even if you only read and work in the sun, you will also be short-sighted.
In recent years, many eye protection lamps on the market do not have much scientific and technological content of their own, nor do they have sufficient theoretical support, but they use people's psychological factors (such as fear of disease, fashion, love of children, etc.) to make profits. Manufacturers use excessively intimidating propaganda to confuse people's ability to judge goods. In fact, as long as we understand some corresponding principles, it is not difficult to use the scientific knowledge we know to make correct judgments.
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