Things to know about ultraviolet (UV)

Ultraviolet (UV) rays are a form of electromagnetic radiation, which helps the skin to synthesize vitamin D, stimulating the body's main activity. In addition, UV rays can also kill bacteria, sterilize, cure psoriasis.

However, excessive exposure to ultraviolet rays can cause serious health problems, and even life-threatening. Here are a few things about UV rays made by LiveScience page:

Some concepts & classification of ultraviolet rays

Electromagnetic radiation comes from the sun and passes through waves or particles at different wavelengths and frequencies. This range of wavelengths is called the electromagnetic spectrum (EM ). The electromagnetic spectrum is divided into seven regions in descending order of wavelength, increasing energy and frequency. Some common wavelengths are radio waves, microwave waves, infrared rays, visible light, ultraviolet rays, X-rays and Gamma rays.

Ultraviolet (UV) rays are electromagnetic waves in the electromagnetic spectrum between visible light and X-rays.

Ultraviolet (UV) rays are electromagnetic waves in the electromagnetic spectrum between visible light and X-rays. Ultraviolet light has a wavelength within the magnetic range (10 nm ÷ 380 nm) corresponding to the 8E14 Hz frequency range. E 3E16 Hz. According to the US Naval UV Radiation Guidelines, based on physiological effects, ultraviolet rays are divided into three categories as follows:

1. UVA rays (400 nm ÷ 315 nm; 3.1 ÷ 3.94eV) or near UV rays.
2. UVB rays (280 nm ÷ 315 nm; 3.94 ÷ 4.43eV) or medium UV rays.
3. UVC rays (180 nm ÷ 280nm; 4.43 ÷ 12.4eV) or UV rays are far away.

The guide also says: "Radiations with wavelengths between 10nm and 180nm are sometimes considered UV vacuum or special UV rays". These wavelengths are blocked by the atmosphere, and they only work & spread in the vacuum.

Application of UV rays during ionization

UV energy is capable of breaking chemical bonds. UV photons, due to more energy, can cause ionization - the process of separating electrons from atoms and creating a gap. This gap affects the biological components of atoms and causes them to make or break chemical bonds that they normally cannot. This may be useful for biological processes, or may also harm living tissue. These effects can be useful, for example, in disinfection, but they can also be harmful, especially to human skin and eyes - the areas most affected by UVB and UVC rays.

Impact of UVA, UVB and UVC rays

According to the National Toxicology Program (NTP) NTP, most exposed human UV rays originate from the sun. However, only about 10% of sunlight is UV, and only 1/3 of this is able to penetrate the atmosphere of the soil cover. Among the UV rays that can reach Earth, 95% are UVA rays and 5% are UVB rays. No studies or measurements have shown the occurrence of UVC in the atmosphere of the earth, because the ozone layer, the atmospheric oxygen and vapor molecules, have absorbed all of the UV rays with short wavelengths. most of this. However, according to NTP's 13th Carcinogen Report: "Broad spectrum ultraviolet radiation - including UVA and UVB rays - are the most harmful and most damaging substances for organisms. on the earth".

Sunburn - a clear demonstration of the impact of UV on humans

Burning is a natural reaction of exposure to toxic UVB rays. Basically, sunburn is the body's natural defense response. Skin consists of melanin pigment cells, which are made of skin from skin cells called melanocytes . Melanin absorbs ultraviolet rays and turns it into heat. When the body senses heat from sunlight, it transfers melanin to surrounding cells and tries to protect them from possible damage. This makes the skin darker.

Skin is the body's natural shield against UV rays.(Image source: Stock.Xchng).

"Melanin is a natural sunscreen," said Gary Chuang, assistant professor of dermatology at Tufts University Medical School in a 2013 interview. However, if the body continues to be exposed to UV rays. , the body's natural defense system can be overwhelmed. Then there will be reactions to toxic substances, leading to sunburn. UV rays can damage the body's DNA cells. The body recognizes this and "sends" blood to the area to help the recovery process. Normally, you only need to be exposed to the sun for half a day, you will feel that your skin is red and has a burning sensation - more or less depends on the sensitivity of each skin.

Sometimes, DNA cells are mutated by UV rays, becoming problematic cells - these cells do not die and even multiply, multiply like cancer cells. Chuang said "UV rays can damage DNA cells as well as the DNA process, making cells capable of being" dead ".

The main results are developed skin cancer - the most common form of cancer in the US in particular and worldwide in general. People who suffer from frequent sunburn are the most at risk for skin cancer. According to Skin Cancer Foundation, the most dangerous form of skin cancer is malignant cancer. This form is twice as likely to happen to people who have been burned 5 times or more than normal people.

Some artificial UV sources

Several artificial sources have been developed & used to produce UV rays. According to the Physical Health Association, "artificial sources include tanning, black light, sterilizer, mercury vapor lamp, halogen lamp, high intensity discharge lamp, fluorescent lamp & hot light, and some other types of laser ".

One of the most common ways to create UV rays is to pass electric current through evaporating mercury or some other gas. This is often used in tanning tools and for surface sterilization. They are also used in black light to make fluorescent paint and glow dyes. LEDs, lasers and arc lamps are also considered as sources of UV with many different wavelengths to be applied in the fields of industry, chemistry, health and applications for research purposes.

Fluorescent - an application of UV rays

Many substances - including minerals, plants, fungi and bacteria, as well as organic and inorganic substances - can absorb UV light. This absorption causes electrons to reach higher energy regions. These electrons will then return to a lower energy level at smaller steps, and emit a small amount of energy from the mass of energy they absorb into visible light. Materials used as dyes or fluorescent paint in the resulting material will be able to glow in sunlight because they absorb invisible UV light and replay it at human wavelengths. OK. For this reason, they become especially useful in making signage, safety warnings and other applications to signal / highlight important announcements.

Fluoride can also be used to locate and identify certain mineral or organic materials. According to Thermo Fisher Scientific, Life Technologies, "Luminous fluorescence allows researchers to detect special components of a complex part of biological molecules, such as living cells, with sensitivity. and high selectivity ".

According to the University of Nebraska, in fluorescent tubes for lighting, "ultraviolet radiation with a 254nm wavelength is generated with blue light emitted when the current is passed through the mercury vapor. This ultraviolet radiation they cannot be seen with the naked eye but they carry more energy than the energy emitted from visible light, the energy from ultraviolet light is absorbed with the fluorine layer inside the fluorescent lamp and replays them in the form of light visible light ". Similar tubes without Flo coating emit UV light that can be used to disinfect surfaces, because the ionizing effects of UV light can kill most bacteria.

In the sun, there are many other sources of UV rays.

Black light tubes often use mercury vapor to produce long wavelength UVA light, making certain substances glow. The glass tube is covered with a dark purple filter material to minimize the visible light source, making the fluorescent light appear more clearly. This filtering is not necessary for applications such as sterilization.

Application of UV rays in astronomy

In the sun, there are many other sources of UV rays. According to NASA, large stars will "glow" within the wavelength of ultraviolet rays. Because the Earth's atmosphere has blocked most of this radiation, especially at short wavelengths, observing stars is done using high-altitude balloons and sympathetic telescopes. dedicated image variable with filter to be observed in the UV region of EM spectrum.

According to Robert Patterson, a professor of astronomy at Missouri State University, most observations are made using charge coupled devices (CCDs) - detectors designed to detect photon short wavelength. These observations can determine the surface temperature of the hottest stars in the universe and reveal the presence of gas clouds between Earth and stellar objects (quasars).

Application of UV rays in the treatment of cancer

According to the UK Cancer Research Association, although exposure to UV rays can cause skin cancer, however, some skin diseases can be treated with ultraviolet rays . In a treatment process called " ultraviolet light treatment (PUVA - psoralen ultraviolet light treatment) , patients are given medication or a cream applied to the skin to make their skin sensitive to light. After that, UV rays will be projected on their skin. PUVA process is used to treat lymphoma (lymphoma), eczema, psoriasis and vitiligo.

It seems that this is a way to counteract the causes of skin cancer to treat skin cancer, but in fact, PUVA method can do this with UV effect on the production. skin cells. It slows down the growth of skin cancer cells, preventing the development of this cancer.

The key to the source of life?

Recent studies show that ultraviolet rays can play an important role in the origin of life on earth, especially the origin of RNA. In an article in the Astrophysical Journal in 2017, the authors of this study noted that red dwarf stars may not emit enough UV rays to "activate" the Biological processes necessary for the formation of ribonucleic acid - a prerequisite for forming all life forms on earth. Studies also suggest that this finding may help in finding life elsewhere in the universe.