Excessive exposure to ultraviolet light can burn the skin, or cause senile cataracts, and even cause skin cancer. However, a moderate amount of ultraviolet light on the human body has many benefits:
Bactericidal disinfection of the human epidermis is distributed in a kind of basal cells, this kind of cell contains "melaninogen" is a tyrosine substance, in the role of ultraviolet light, "melaninogen" into black, deposited in the sunburned skin. Under the action of ultraviolet rays, "melaninogen" becomes black and deposits on the surface of the sunburned skin, making the skin a uniform dark brown color. This is an important reason for sun tanning. This kind of pigmentation can absorb more light energy, quickly transformed into heat energy, and stimulate the secretion of sweat glands and heat dissipation. Sun exposure can kill bacteria on the skin and prevent boils, folliculitis and other skin diseases. Indoor often into the sunshine, diligent sun bedding, can reduce the spread of disease.
Promoting calcium and phosphorus metabolism of human skin contains steroids, this material by the sun's ultraviolet radiation can be changed into vitamin D. Vitamin D into the blood to improve the metabolism of calcium and phosphorus, anti-rickets, osteomalacia and osteoporosis in the elderly role.
Enhancement of the body's immune system UV radiation in the sun can stimulate the body's hematopoietic function, so that the number of red blood cells increased, the increase in hemoglobin, improve the quality of red blood cells, improve the state of muscle activity, but also reduce blood pressure, blood sugar, cholesterol, increase the body's immune system, to promote the body's cellular oxygen uptake capacity and metabolism, to alleviate asthma and joint pain, soothing and revitalizing the blood and enhance the quality of body.
So what time should I receive UV rays? In the height of summer 11-17 hours should not receive sunlight, because this time infrared rays are too strong, generally can reach more than 1.5 calories per minute per cubic meter, the resulting temperature is 37 ℃ -45 ℃. Spring and fall season 7-10 o'clock, or 15-16 o'clock, this time, the sun's ultraviolet rays are strong, infrared rays are weak.
While excessive ultraviolet rays cause harm to the human body, the human body can not grow healthily without ultraviolet rays. The 7-dehydrocholesterol in the skin is converted into vitamin D3 by light irradiation. Vitamin D3 has an important physiological function in maintaining the concentration of calcium ions inside and outside the body's cells and in regulating calcium and phosphorus metabolism. In countries with insufficient sunshine, rickets in infants and young children and adult osteomalacia and osteoporosis onset of more than one, the infant's thriving cannot be separated from the right amount of sunbathing, the human body needs the right amount of ultraviolet light, therefore, the right amount of light is still necessary.
Outside the red light, invisible to the naked eye, with a thermal effect of light called infrared.
It is longer than the wavelength of visible light, invisible to the naked eye light segment, infrared light is the sun's rays in the many invisible light in one of the German scientists H?sschel in 1800, also known as infrared thermal radiation, the wavelength of infrared light on the solar spectrum is greater than that of the visible light, with a wavelength of 0.75 ~ 1000 μm. infrared light can be divided into three parts, namely, the near-infrared light, with a wavelength of The infrared can be divided into three parts, namely, near-infrared, with a wavelength of 0.75 to 1.50 μm; mid-infrared, with a wavelength of 1.50 to 6.0 μm; and far-infrared, with a wavelength of 6.0 to l000 μm.
The real infrared night vision is photomultiplier tube imaging, and the principle of the telescope is completely different, can not be used during the day, expensive and need power to work.
The wavelength of ultraviolet light is shorter than infrared light, infrared light in the visible band of red light outside, ultraviolet light in the visible band of violet light outside the measurement. Infrared light is mainly thermal effect, can be used for heating, the detection of infrared intensity can also be used to identify objects. Ultraviolet light can use its short wavelength, high frequency, high energy characteristics of sterilization, chemical catalysis and other work
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