Social Studies-Today and Yesterday in My Hometown 1500 I am Linqu, Weifang, Shandong! ! ! Xinhua Middle School! ! ! This assignment will not write the amount. ...

The spring breeze of reform is blowing all over China, and the fire of reform and opening up is burning all over my hometown, making my hometown, Gaotang, look like a vibrant girl, very cute.

According to my father, my hometown used to be a small bungalow next to me, so it would be nice to have a two-story building. The road is very narrow, and only three or four bicycles can walk side by side. It's muddy when it rains. As for squares and entertainment places, people have never even heard of them.

Now, high-rise buildings are springing up like mushrooms after rain, towering into the sky, the characteristics of a building, and the posture of a building. There are many entertainment places, among which there are several light squares: Jincheng Square is a good place for people to play, especially in summer nights. Many people are watching TV in front of the big screen in the south of the square, while teenagers are listening to beautiful and moving music in the music fountain, which makes people linger. Memorial Square is different. In the square, people feel like heroes, as if the revolutionary martyrs are really alive and living in people's hearts! Although the cultural square has not been built yet, it is very beautiful. The square at night is full of colorful lights, and it is extremely elegant to walk in it!

The biggest change in my hometown is that river. It used to be smelly and full of garbage, but now it has become a beautiful river. But light pollution is a new environmental pollution source after waste gas, waste water, waste residue and noise, mainly including white light pollution, artificial daytime pollution and colored light pollution. Light pollution is threatening people's health.

White light pollution In the busy streets of the city, many shops decorate their facades with large mirrors or aluminum alloys, and some even decorate their facades with mirrors from top to bottom. People are almost in a mirror world and can't tell the direction. In the season of strong sunshine, the decoration of tempered glass, glazed tile wall, aluminum alloy plate, polished granite, marble and high-grade paint is dazzling. According to the measurement, the reflection coefficient of white paint surface is 69 ~ 80%, while that of mirror glass is 82 ~ 90%, which is about 10 times larger than that of buildings decorated with green grass, forest, dark or rough masonry, which greatly exceeds the human body's tolerance and becomes one of the new pollution sources in modern cities. White light pollution will damage the cornea and iris of human eyes, resulting in decreased vision and increased incidence of cataract.

Man-made daytime pollution When night falls, billboards and neon lights in hotels and shopping malls are dazzling, and some strong beams even go straight into the sky, making the night like day. Artificial sunlight also has adverse effects on people's physical and mental health. Due to the strong light reflection, the nearby rooms can shine like daytime, making it difficult for people to fall asleep at night, disrupting the normal biological rhythm and leading to listlessness. According to a survey abroad, two-thirds of people think that artificial daytime affects their health, and 84% of them report that it will affect their sleep at night. In order to avoid glare, people have to close bedroom windows or install dark curtains. Artificial sunlight can also harm insects and birds, because strong light will destroy the normal reproduction process of nocturnal insects. At the same time, insects and birds will be burned to death by the high temperature around strong light.

Color light pollution The black lights, rotating movable lights, fluorescent lights and flashing color light sources installed in modern dance halls constitute color light pollution, which is harmful to human health. According to the measurement, black light can produce ultraviolet with the wavelength of 250 ~ 320 nm, and its intensity is much higher than that in sunlight. If the human body is exposed to this black light for a long time, it may induce nosebleeds, tooth loss, cataracts, and even leukemia and cancer. The harmful effect of this ultraviolet ray on human body can last for 15 ~ 25 years. Rotating movable lights and colored light sources are dazzling, which is not only bad for eyes, but also interferes with the central nervous system of the brain, causing dizziness, instability, headache, insomnia, inattention, loss of appetite and other symptoms. The flashing neon lights in the ballroom will not only damage people's visual function, but also disturb the internal balance of the human body, making the body temperature, heartbeat, pulse and blood pressure uncoordinated, causing light damage syndrome such as dizziness, irritability, loss of appetite, fatigue and insomnia. Excessive exposure to fluorescent lamps will reduce the body's ability to absorb calcium, leading to calcium deficiency.

Now some luxurious dance halls are equipped with laser devices. According to the investigation and measurement of laser equipment in dozens of dance halls by relevant health departments, the laser radiation pressure in most dance halls has exceeded the limit. When this high-density thermal beam passes through the lens of the eye and focuses on the retina, the temperature of the focusing point can reach 70 degrees Celsius, which is very harmful to the eyes and brain nerves. It will not only damage people's eyesight, but also cause brain central nervous system diseases such as headache, dizziness, cold sweat, neurasthenia and insomnia.

The latest research by scientists shows that colored light pollution not only damages people's physiological functions, but also affects people's psychology. The measurement of "Chromaticity Effect of Spectral Light" shows that if the psychological effect of white light is 100, blue light is 152, purple light is 155, red light is 158, and black light is the highest, which is 187. If people are exposed to colored lights for a long time, their psychological accumulation effect will also cause burnout, dizziness, loss of libido, impotence, irregular menstruation, neurasthenia and other physical and mental diseases to varying degrees.

At present, although light pollution is not included in the prevention and control of environmental pollution, its harm is obvious, and there is a trend of aggravation and spread. Light pollution has attracted more and more attention of scientists, who are trying to study ways to prevent light pollution. People should also pay attention to prevent all kinds of light pollution from harming health and avoid being exposed to light pollution for too long. We should actively create a beautiful and comfortable environment and minimize the threat of light pollution.