Shandong Underwater Photography Competition

At about 3 pm on July 27th, a brief Tindal effect was staged over Jinan. Sunlight shines through the clouds, and the integrated beam is beautiful!

The air quality in Jinan is really not very good. Let's just check. Jinan is one of the cities with poor air quality in China, which has a lot to do with its geographical location. Shandong province is a big industrial province with heavy industrial pollution and insufficient urban greening area. In addition, Jinan is surrounded by mountains on three sides, and the air circulation is poor. In winter, the wind in the north can't blow out and the wind in the south can't blow in. So the sky in Jinan is always surrounded by a thick layer.

Of course, some people have another saying about the poor air quality in Jinan, that is, poor environmental planning and industrial pollution, especially on the north-south road where industries are concentrated. Jinan's industries have high air emissions, and the air quality is naturally worse. Jinan is also a city with a large population. Automobile exhaust, domestic coal burning, and a lot of smoke and dust are discharged into the air. In addition, the vegetation coverage rate is too low, causing serious environmental pollution. It is impossible to throw all the pots on the terrain.

The dazzling scattered light instantly covers Tindal effect over Jinan, which is actually a darkroom phenomenon. Simply put, light depends on fog or dust in the atmosphere. When the sun shines on it, the lines of light can be clearly seen, and the sun is a large area of light, so this very magnificent light is formed. This phenomenon is called "Jesus light" abroad, because when this phenomenon appears, sunlight passes through the clouds to form a large light channel, which is very spectacular, just like a myth.

Of course, the air quality in Jinan has improved, but because it is an old city, it is still difficult to rectify it. Many people say that Jinan doesn't know why there are so many roads to be rebuilt, and it has been in a dusty environment. Therefore, when netizens saw the "Tingdahl effect" over Jinan, they couldn't help saying that the blue of Jinan is back!

The reason for the Tyndall effect is that when a beam of light passes through the colloid, a bright "channel" can be observed in the colloid from the direction perpendicular to the incident light. The appearance of Tindal effect also implies that light can be seen.

In the process of light propagation, when light shines on particles, if the particles are many times larger than the wavelength of incident light, light reflection will occur; If the particles are smaller than the wavelength of the incident light, light scattering will occur. What is observed at this time is the light radiated by light waves around the particles, which is called scattered light or milky light. Tindal effect is a phenomenon of light scattering or milky light. Because the diameter of true solution particles is generally less than 1nm, colloidal particles are between solute particles and suspension particles in the solution, and their diameter ranges from 1 ~ 100nm.

It is less than the wavelength of visible light (400 nm ~ 700 nm), so when visible light passes through colloid, it will have obvious scattering effect. For real solution, although the molecules or ions are small, the intensity of scattered light decreases obviously with the decrease of the volume of scattered particles, so the scattering effect of real solution on light is very weak. In addition, the intensity of scattered light also increases with the increase of particle concentration in the dispersion system.

So the colloid can have Tindal phenomenon, but the solution hardly has it. Tindal phenomenon can be used to distinguish colloid from solution. Note: when the light passes through the suspension, sometimes there will be a light path, but the particles in the suspension hinder the light too much, making the light path very short.