Write an expository essay on the topic of absence of light

The Dangers of Light PollutionWithout light there would be no color, and everything in the world would be pitch black. For human beings, light is as indispensable as air, water and food. Eyes are the most important sense organs of the human body, the human eye on the light of the adaptability of the strong, the pupil can be adjusted with the brightness of the environment. However, if you look at things in low light for a long time, your eyesight will be damaged. On the contrary, strong light can make the human eye instant blindness, or cause permanent damage. People must work, study and live in a suitable light environment. On the other hand, human activities may cause damage to the surrounding light environment, so that the original suitable straight light environment becomes uncomfortable straight, which is light pollution. Light pollution is a special form of pollution, which includes visible light, laser, infrared and ultraviolet light pollution. Visible light pollution is more common is glare. For example, whenever you walk along the road at night, the oncoming headlights of motor vehicles shake the pedestrians so that they can not open their eyes, which is a kind of light pollution, called glare. This dazzling light source is not only common on the road, in some industrial and mining enterprises are often seen. Such as in the melting, smelting and welding process, very strong light is also harmful light pollution. Visible light pollution is more dangerous is the explosion of nuclear weapons glare. It can cause eye damage to a considerable range of people. If there is no appropriate protective measures, long-term welding, smelting and melting glass and other work, the eyes will be harmed, blind spots in the eyes, to the old easily suffer from cataracts, which is the result of strong light damage to the lens of the eye. Modern urban light pollution with the increasing development of modern cities and prosperity, a new urban light pollution is threatening human health. This new urban light pollution is: urban, downtown shopping malls, companies, office buildings, restaurants, hotels, restaurants; hair salons and dance halls, etc. are using large pieces of mirrored glass, stainless steel panels and aluminum alloy doors and windows decorated. Some even from the neck item to the bottom of all with mirror glass mounted clear, so that people seem to be in the world of mirrors, the direction is difficult to defend, and thus accidents. After sunset, nightfall, the city's busy streets on a variety of billboards, neon lights, waterfall lights and so on are lit up, colorful, so that people fork in the artificial daytime. Into the modern ballroom, people for the pursuit of stimulation, often using "color light source", "sunshine light source", "rotating light source", etc., dazzling. For these sources of light pollution, domestic and foreign scientists believe that urban light pollution can seriously interfere with people's nervous system, so that the normal visual activities of people affected. In the season of strong sunlight, the building's mirror glass, glazed tiles, stainless steel, aluminum alloy plate, polished granite, marble and high-level coating poles and other decorative, bright, since the flowers, dazzling pharyngeal forced people. According to scientific determination, the light reflection coefficient of these decorative materials are more than 69%, and even up to 90% demolition, than green areas, forests, dark or hairy masonry outside the decorative building reflection coefficient is about 10 times larger than the human body can withstand the limit, and lead to dizziness, headache, nervousness, inattention, annoyed manipulation of palpitations, insomnia, loss of appetite, fatigue, and other discomforts, and will also Induce photosensitive dermatitis, harm the human cornea and iris, bow l up vision loss. Artificial since the Qui on the physical and mental health of people can not be ignored, reflecting light into the room, destroying people's circadian rhythms, making it difficult to sleep, and even lead to insomnia and neurasthenia, resulting in sleepiness, easy to go to work, accidents and other safety aspects. Laser pollution laser is issued by the laser a special light, it's a single color, light Harvest straight, great intensity. At present, the laser has thousands of colors, has many advantages, and has been widely used. But because of the laser's energy concentration, high brightness, so more harm than other light. Laser energy such as continuously issued, the maximum power up to tens of thousands of kilowatts, the instantaneous power up to trillions of kilowatts, children's seconds can be a thick steel plate through, not to mention people. Therefore, the laser fork is known as dead light. Laser environmental pollution caused by two aspects: is the laser beam through the air so that many substances (such as dust) gasification, resulting in atmospheric pollution; on the other hand, the laser will not only harm the eye's conjunctiva, iris and lens, but also may be directly harmful to the body's deep tissues and nervous system. At present, lasers are mainly used in laser industry (cutting, punching, etc.), mapping, medical treatment and scientific research. Infrared pollution infrared in the military, artificial satellites, as well as industry, agriculture, health research and other aspects have a wide range of applications. Infrared pollution can not be ignored. Infrared is a kind of invisible light, its main role is the role of heat, stronger infrared light irradiation of the human body, can cause skin damage, skin burns similar to scalding. Infrared rays are likewise injurious to the human eye; they can harm the retina at the bottom of the eye, and may also cause corneal burns and iris injuries. Ultraviolet Pollution Ultraviolet light is also a type of invisible light, which has a wide range of applications in production, defense, and medicine. For example, disinfection, sterilization, treatment of certain skin diseases and chondromalacia, etc. It is also used in the detection of artificial satellites on the ground. But the harm of ultraviolet light on the human body, mainly harm to the human eyes and skin, long-term excessive exposure to ultraviolet light, will make the cornea of the eye cornea show cornea from the rabbit injury, will make the skin appear "light dermatitis, in serious cases, will make the skin peeling necrosis, and even cause skin cancer. Ultraviolet light is also a kind of light pollution that harms the skin. [edit paragraph] What is light pollution light pollution problem was first raised in the 1930s by the international astronomical community, they believe that light pollution is the city outdoor lighting to make the sky bright caused by the negative impact on astronomical observation. It was later called "disturbing light" in the United Kingdom and the United States, and "light pollution" in Japan. At present, there is no clear definition of light pollution at home and abroad. Now it is generally believed that light pollution refers to a variety of light that affects the natural environment, adversely affects the normal life, work, rest and recreation of human beings, impairs people's ability to observe objects, causes discomfort and harms human health. Light radiation from a wavelength of ten nanometers to one millimeter, i.e., ultraviolet radiation, visible light and infrared radiation, can be a source of light pollution under different conditions. Broadly speaking, light pollution includes a number of things that may have an adverse effect on the visual environment and physical health, including the common life of books and paper, wall paint reflections and even colorful roadside advertisements "light" can also be counted in this list, light pollution contains a wide range of this can be seen. In daily life, people commonly see light pollution as a result of mirrored architectural reflections that cause dizziness for pedestrians and drivers, as well as the discomfort caused by unreasonable lighting at night. [edit paragraph] Classification of light pollution according to different classification principles, light pollution can be divided into different types. Internationally, light pollution is generally divided into three categories, namely, white light pollution, artificial daytime and colored light pollution. 1. white light pollution when the sunlight irradiation is strong, the city buildings of the glass curtain wall, glazed brick walls, polished marble and a variety of paints and other decorative reflective light, bright white, dazzling. Expert research has found that long time in the white light pollution environment work and life, retina and iris will be subject to varying degrees of damage, sharp decline in visual acuity, cataract incidence rate of up to 45%. Also make people dizzy and upset, and even insomnia, loss of appetite, depression, physical weakness and other symptoms similar to neurasthenia. In summer, the glass curtain wall of strong reflected light into the nearby residential buildings, increasing the indoor temperature, affecting normal life. Some glass curtain walls are semi-circular, reflected light convergence is also easy to cause fire. Driving under the hot sun driving drivers will be surprised by the glass curtain wall reflected light of the sudden attack, the eyes are strongly stimulated, it is easy to induce car accidents. According to optical experts, the mirror building glass reflected light than sunlight is more intense, its reflectivity of up to 82% to 90%, the light is almost fully reflected, much more than the human body can withstand the scope. Prolonged in the white light pollution environment of work and life, easy to lead to vision loss, produce dizziness, insomnia, palpitations, loss of appetite and depression and other symptoms similar to neurasthenia, so that people's normal physiological and psychological changes in the long term will induce certain diseases. Expert research has found that a long time in the white light pollution environment work and life, retina and iris will be subject to varying degrees of damage, sharp decline in visual acuity, the incidence of cataracts up to 45%. In summer, the glass curtain wall strong reflected light into the nearby residential buildings, destroying the original good indoor atmosphere, but also make the room temperature on average 4 ℃ ~ 6 ℃. Impact on normal life. * Glare pollution headlamps used for lighting when cars are traveling at night, unreasonable lighting arrangements in factories, etc. can cause glare. In certain workplaces, such as train stations and airports and the central control rooms of automated businesses, excessive and overly complex signaling systems can also cause a decline in the visual acuity of staff, thus affecting work efficiency. The glare produced by welding torches can also harm the eyes if proper protection is not provided. Long-term workers in the bright light conditions (such as smelters, burners, glass blowers, etc.) will also be due to the glare and eye damage. 2. Artificial daytime nightfall, shopping malls, hotels on the advertising lights, neon lights flashing eye-catching, dazzling. Some of the strong beams of light and even straight into the sky, making the night as the day, the so-called artificial day. In such a "night city", it is difficult to sleep at night, disrupting the body's normal biological clock, resulting in low efficiency during the day. Artificial daytime also harms birds and insects, and bright light may disrupt the normal breeding process of insects at night. At present, the widespread and excessive use of lights in big cities makes the sky too bright to see the stars, affecting astronomical observation, aviation, etc. Many observatories are forced to stop working as a result. According to astronomical statistics, the sky at night without light pollution, you can see the stars of about 7,000, while in the street lamps, background lights, landscape lights shooting the big city, can only see about 20 ~ 30 stars. 3. colored light pollution dance halls, nightclubs installed black lights, rotating lights, fluorescent lights, and flashes of colored light source constitutes a colored light pollution. It has been determined that the intensity of ultraviolet light produced by the black light is much higher than the ultraviolet light in the sun, and the harmful effects on the human body lasts for a long time. If a person receives this kind of irradiation for a long time, it can induce nosebleeds, tooth loss, cataracts, and even lead to leukemia and other cancers. Colored light source dazzling, not only for the eyes, and interfere with the central nervous system of the brain, make people feel dizzy, nausea and vomiting, insomnia and other symptoms. Scientists have shown that the latest research, colored light pollution is not only detrimental to human physiological functions, but also on the human psyche has an impact. "Spectral light chromaticity effect" measurement shows that, such as the psychological impact of white light for 100, the blue light for 152, purple light for 155, red light for 158, black light is the highest, for 187. if people are in the long term in the irradiation of colored light, its psychological cumulative effect, but also varying degrees of fatigue caused by weakness, dizziness, Loss of libido, impotence, menstrual disorders, neurasthenia and other physical and mental disorders. In addition, some scholars also according to the size of the scope of the impact of light pollution Jiang light pollution is divided into "outdoor visual environment pollution", "indoor visual environment pollution" and "local visual environment pollution". Among them, the outdoor visual environmental pollution, including building facades, outdoor lighting, etc.; indoor visual environmental pollution, including indoor decoration, indoor poor light color environment, etc.; local visual environmental pollution, including books and paper and some industrial products, etc. * Laser pollution laser pollution is also a special form of light pollution. Due to the laser has a good direction, energy concentration, color and other characteristics of pure, and laser through the human eye lens focusing effect, to reach the fundus of the light intensity can be increased by hundreds to tens of thousands of times, so the laser on the human eye has a greater role in the damage. Part of the laser spectrum is in the ultraviolet and infrared ranges, which can damage the conjunctiva, iris and lens. Very powerful lasers can harm the deep tissues of the body and the nervous system. In recent years, laser in medicine, biology, environmental monitoring, physics, chemistry, astronomy and industry and other aspects of the application of the increasingly wide range of laser pollution is more and more people pay attention to. *Infrared pollution infrared in recent years in the military, artificial satellites, as well as industrial, health, scientific research and other aspects of the application of the increasingly widespread, so infrared pollution problems also arise. Infrared is a kind of thermal radiation, the human body can cause high-temperature damage. Stronger infrared rays can cause skin injuries similar to scalds, initially burning and then causing burns. Infrared damage to the eye has several different situations, the wavelength of 7500 ~ 13000 ? of infrared light on the cornea of the cornea of the higher transmittance, can cause damage to the fundus of the retina. Especially near 11000 ? infrared, can make the front of the eye medium (cornea, crystal, etc.) is not damaged and directly caused by the fundus retinal burns. Infrared wavelength of 19000? or more, almost all absorbed by the cornea, will cause corneal burns (clouding, white spots). The energy of infrared rays with wavelengths greater than 14,000 ? is mostly absorbed by the cornea and intraocular fluid, and does not penetrate the iris. Only infrared rays below 13,000 angstroms can penetrate the iris and cause iris damage. Prolonged exposure of the human eye to infrared light may cause cataracts. *UV PollutionUltraviolet light was first used for sterilization and in certain processes. In recent years it has been used in a wider range of applications, such as for ground detection by artificial satellites. The effect of ultraviolet light varies according to its wavelength. The vacuum ultraviolet part with a wavelength of 1,000 to 1,900 angstroms can be absorbed by air and water; the far-ultraviolet part with a wavelength of 1,900 to 3,000 angstroms, most of which can be strongly absorbed by biomolecules; and the near-ultraviolet part with a wavelength of 3,000 to 3,300 angstroms, which can be absorbed by certain biomolecules. Ultraviolet light on the human body mainly harms the cornea and skin. The UV rays that cause damage to the cornea are mainly the 2500-3050? portion, and the wavelength of 2880? has the strongest effect. Multiple exposures of the cornea to UV do not increase tolerance to UV. The damaging effects of UV on the cornea manifest themselves in an extremely painful corneal leukoplakia injury called photophobia. In addition to severe pain, it results in tearing, blepharospasm, conjunctival congestion, and ciliary muscle twitching. The injurious effects of ultraviolet rays on the skin are mainly to cause erythema and small blisters, and in severe cases necrosis and desquamation of the epidermis. The skin on the chest, abdomen and back of the human body is the most sensitive to ultraviolet light, followed by the forehead, shoulders and buttocks, and then the palms of the feet and the back of the hands. The effect of different wavelengths of ultraviolet light on the skin is different, the wavelength of 2800 ~ 3200 ? and 2500 ~ 2600 ? of ultraviolet light on the skin of the strongest effect. Broad light pollution also includes: visual pollution refers to the cluttered visual environment in the urban environment. For example, the city streets on both sides of the messy wires, telephone lines, cluttered garbage waste, messy stalls and colorful advertising posters and so on. There are many other ways to categorize light pollution, for example, in Wikipedia, we see light pollution is divided into the following categories: Lighttrespass This kind of "pollution" is mainly refers to the overpowering light source affecting the daily rest of others. For example, the lights at night make it difficult to sleep, and so on. Currently, countries have laws to protect their people from light trespass. over-illumination (over-illumination) Over-illumination is the waste of energy caused by the pointless use of energy. The amount of energy wasted in the United States every day due to "over-illumination" is equivalent to 2 million barrels of oil! Clutter (混光) The mixing of different kinds of light sources together will seriously affect the passive recipient. Clutter (mixing of light sources) is a serious problem for passive recipients and can lead to car accidents. What's worse, for pilots flying at night, it takes energy to find and recognize aviation signals among these various kinds of light.Glare (glare) Bright light in the dark. Glare is a bright light in the dark that can cause pedestrians or drivers to lose their vision for a short period of time, which can lead to traffic accidents. In addition, if not properly protected, this glare can also harm human eyesight. skyglow (artificial daytime phenomenon) artificial daytime will seriously affect the work of astronomers, and ecological damage. In short, light pollution leads to waste of energy and damages the physical and mental health of human beings. In addition, excessive light pollution can seriously damage the ecological environment and have a negative impact on traffic safety and aerospace science research. Before the government effectively adjusts the light source, we must pay attention to stay away from similar sources of pollution. China's Tianjin University Professor Ma Jian is easy to light pollution occurs and caused by the impact of time as a classification standard, light pollution is divided into "daylight light pollution" and "night light light pollution", before the white light pollution belongs to the daylight light pollution, artificial daylight and colored light pollution belongs to the Artificial daytime and colored light pollution belongs to night light pollution. Artificial daylight and colored light pollution are classified as night light pollution. [Edit paragraph] the harm of light pollution light pollution so that one-fifth of the world can not see the Milky Way according to the United States of America, a new research study shows that the night lights caused by light pollution has made one-fifth of the world's people to the Milky Way out of sight. "Many people have lost the night sky, and it is our lights that make the night sky lose its color," said Elvidge, one of the authors of the survey. He believes that about two-thirds of the world's population now lives with light pollution. In the night sky in the countryside away from the city, more than two thousand stars can be seen, while in the big cities only a few dozen can be seen. In Europe, America and Japan, the problem of light pollution has long been a cause for concern. The United States also established the International Dark Night Sky Association, specializing in the fight against light pollution. Myopia and the environment related to noise and light pollution is damaging your eyes and mine people know that water pollution, air pollution, noise pollution on human health hazards, but did not find around the potential threat - noise and light pollution, is seriously damaging to people's eyes. In recent years, environmental pollution is increasing. Countless tragedies have occurred, so that people increasingly understand the importance of the environment to human survival and health. People are concerned about water pollution, air pollution, noise pollution, etc., and take measures to vigorously rectify, but the noise and light pollution is not enough attention. The consequence is a variety of eye diseases, especially myopia rate is rapidly rising. According to statistics, China's high school students myopia rate of more than 60%, ranking second in the world. To this end, our country every year to invest a lot of money and manpower to deal with myopia, but the effect is not big, the reason is not from the improvement of the visual environment as a fundamental starting point. The relevant health experts believe that the visual environment is the main reason for the formation of myopia, rather than eye habits. According to relevant experts, the visual environment of noise and light pollution can be broadly divided into three kinds: one is the outdoor visual environment pollution, such as building facades; two is the indoor visual environment pollution, such as indoor decoration, indoor poor light color environment; three is the local visual environment pollution, such as books and paper, some industrial products. With the development of urban construction and scientific and technological progress, daily life in the building and interior decoration using mirrors, ceramic tiles and whitewashed walls are increasing, close reading and writing the use of books and paper more and more smooth, people almost put themselves in a "strong light and weak color" of the "man-made visual environment People almost put themselves in an "artificial visual environment" with "strong light and weak colors". At present, few people recognize the harm of noise light pollution. According to scientific determination: general white powder wall light reflection coefficient of 69-80%, mirror glass light reflection coefficient of 82-88%, especially smooth powder wall and white book paper light reflection coefficient as high as 90%, higher than the grass, forests or hairy decorative surface of about 10 times, this value is much more than the human body can withstand the Physiological adaptation range, constituting a new source of modern pollution. The research shows that the noise light pollution can cause damage to the cornea and iris of the human eye, inhibit the retinal photoreceptor cell function play, cause visual fatigue and vision loss. According to the relevant health departments of dozens of cabaret laser equipment to do the investigation and determination shows that the vast majority of cabaret laser radiation pressure has exceeded the limit value. This high density of thermal light beam through the eye lens and then focus on the retina, the temperature of its spotlight can reach 70 degrees Celsius, which is very harmful to the eyes and brain nerves. It can not only lead to people's eyesight is damaged, but also make people have headaches and dizziness, cold sweat, neurasthenia, insomnia and other diseases of the central nervous system of the brain. Scientists have shown that the latest research, colored light pollution is not only detrimental to human physiological functions, but also on the human psyche has an impact. "Spectral light chromaticity effect" measurement shows that, such as the psychological impact of white light for 100, the blue light for 152, purple light for 155, red light for 158, black light is the highest, for 187. if people are in the long term in the irradiation of colored light, its psychological cumulative effect, but also varying degrees of fatigue caused by weakness, dizziness, Loss of libido, impotence, menstrual disorders, neurasthenia and other physical and mental disorders. The visual environment has been a serious threat to the healthy life and work efficiency of human beings, causing a lot of losses to people every year. For this reason, attention to visual pollution, improve the visual environment, has been urgent. Artificial daylight can also harm insects and birds, as bright light can disrupt the normal reproductive processes of nocturnal insects. At the same time, insects and birds can be burned to death by the high temperatures surrounding the bright light. Light pollution also disrupts the biological clock rhythms in plants, hindering their growth and causing their stems or leaves to become discolored or even die; it affects the formation of flower buds, and can affect dormancy and the formation of winter buds. [edit paragraph] Light pollution prevention and control of light pollution prevention and control of the following aspects: ① Strengthen urban planning and management, improve factory lighting conditions, etc., in order to reduce the source of light pollution. ② Infrared and ultraviolet pollution of the place to take the necessary safety measures. ③ Use personal protective measures, mainly wearing protective glasses and protective masks. Light pollution protective goggles reflective protective goggles, absorptive protective goggles, reflective-absorptive protective goggles, explosive protective goggles, photochemical reaction protective goggles, photoelectric protective goggles, color-changing microcrystalline glass type protective goggles and other types. Although light pollution has not been included in the scope of environmental control, its harm is obvious and is increasingly aggravating and spreading. Therefore, people should pay attention in their lives to prevent the health hazards of various kinds of light pollution and avoid prolonged exposure to pollution. Light pollution of the environment is the actual existence, but due to the lack of corresponding pollution standards and legislation, and thus can not form a more complete environmental quality requirements and preventive measures. Prevention and control of light pollution, is a social and systematic project, need to play the relevant departments to develop the necessary laws and regulations, to take appropriate protective measures. First of all, in the enterprise, health, environmental protection and other departments, we must have a clear understanding of light pollution, we must pay attention to the control of the source of light pollution, we must strengthen preventive health supervision, so as to prevent the problem before it occurs; scientific and technological researchers in science and technology should also explore ways to reduce light pollution. In the design program, the rational choice of light sources. To educate people scientifically rational use of light, pay attention to adjust the brightness, do not abuse the light source, do not expand the light pollution. Secondly, for individuals to increase environmental awareness, pay attention to personal health care. Individuals who can not avoid long-term light pollution in the work environment, should take into account the issue of preventing light pollution, the use of personal protective measures: wearing protective goggles, protective masks, protective clothing and so on. Eliminate the hazards of light pollution in the bud. Symptoms have appeared should regularly go to the hospital ophthalmology examination, timely detection of the disease, prevention-oriented, prevention and treatment.