Learn about electromagnetic spectrum
We humans now see, feel, and even everything related to eating, drinking and nearly every activity has the presence of electromagnetic waves. Why do you say that? Because electromagnetic waves pervade every part of our world, as long as the temperature is above absolute zero, any object will have electromagnetic radiation.
Electromagnetic waves are transmitted by photons, so they can also be called light waves. But this light wave is divided into visible light and invisible light, in daily life, light wave generally only refers to the visible light part of the electromagnetic spectrum, and visible light only a small part of the electromagnetic spectrum. The longest wavelengths of electromagnetic waves are several kilometers or even longer, the shortest are less than 1 angstrom, and the shortest are gamma rays.
Electromagnetic waves have wavelength and frequency, and wavelength is inversely proportional to frequency, i.e. the longer the wavelength and the smaller the frequency, the smaller the energy, and vice versa. The relationship between the wavelength and frequency of an electromagnetic wave is: c = λf. Here c is the speed of light, λ is the wavelength and f is the frequency. The longest electromagnetic wave wavelengths are radio waves (including long waves, medium waves, short waves, microwaves), then from long to short: infrared rays, visible light, ultraviolet rays, X-rays, γ-ray.
The wavelengths of radio waves are in the order of kilometers to millimeters, the wavelengths of long waves can reach several kilometers, and the shortest microwave wavelengths are only 0.1 mm; the wavelength of visible light is between 760nm and 380nm, nm is nanometer – 1mm = 1000μm (micrometer), 1μm = 1000nm, 1nm = 10^-9m (meter).
The wavelengths of ultraviolet, X-rays and gamma rays are much shorter.
All matter in this world vibrates and therefore has a frequency. Frequency is the number of times an object vibrates in one second, and the frequency of an electromagnetic wave is the number of times the electromagnetic wave vibrates in one second, in Hz (Hertz). The frequency of radio waves ranges from 1000Hz to 10^9Hz; the frequency range of visible light ranges from 3.9 x 10^14 to 7.7 x 10^14Hz; the frequency range of gamma rays is 10^12Hz to 10^30Hz.
To make it easier to imagine, it can be visualized that the size of the coronavirus is about 100 nm, however the size of the longest gamma ray band is only 0.1 nm – 1,000 times smaller than that of the coronavirus, and its frequency is more than a thousand. billion times per second. Therefore, it can be said that gamma rays are the most powerful “light” in the universe, but this light is invisible and kills humans.
The principle of harm of gamma rays to living things
Due to their very short wavelength and extremely high energy, gamma rays can penetrate the body of any living being. All living things are made up of cells, and at the core of each cell is the genetic material DNA. For example, the human body consists of 40 to 60 trillion cells. The largest cell is the oocyte, and the mature oocyte is 200 μm (microns); The smallest cells are platelets, only about 2 μm in diameter.
When the human body is irradiated with rays, the rays will enter human cells and ionize with the cells, penetrate into the complex organic molecules in the cells, and destroy the cell tissues. The most important core genetic material in a cell is DNA, which is a macromolecule with a double helix structure.
This DNA double helix unfolds is about 2m long. If all the DNA in a human cell were open and connected, it is said that it could travel from Earth to the sun more than 300 times. But the DNA helices are only 2nm in diameter, and gamma rays can disrupt and disrupt their structure. Therefore, when an organism is irradiated with gamma rays, the molecular bonds of its DNA are broken, rendering the organism incapable of survival.
When the amount of radiation is large, the organism will die immediately, even if the radiation is not large, the molecular bonds of the DNA in the body are also seriously damaged and will die gradually.
Principle of gamma rays
Radionuclides will produce a new nucleus after alpha decay and beta decay. Gamma rays occur in both nuclear fusion and nuclear fission, so the universe is filled with gamma-ray radiation.
The sun’s nuclear fusion continues in the core within a quarter of the volume radius. The main process is the chain reaction of protium, from protium to deuterium to helium-3, and finally to helium-4. The result is the fusion of four protium nuclei into one helium-4 nucleus, releasing gamma photons, neutrinos, and positrons in the process. Neutrinos quickly escape from the surface of the sun into space thanks to strong penetration, but it is not easy for gamma rays to carry huge energy to escape.
This is related to the theory of photons traveling inside the sun. The propagation characteristic of photons in a vacuum is the fastest, reaching 300,000 km/s. The interior of the sun is filled with protons, and photons collide with protons in their every step, constantly colliding and exchanging. Therefore, for these photons to pass through the sun, they must travel with a radius of 700,000 km, and must collide and exchange with protons about 10^26 times, so it takes hundreds of thousands or even millions of years. , the new photons can reach the surface of the sun.
So don’t be surprised, the sunlight hitting us is actually photons born hundreds of thousands or even millions of years ago.
According to scientific analysis, sunlight covers the entire electromagnetic wave band, but more than 99.9% of the energy is concentrated in the 200 ~ 10000nm wavelength range, and the maximum radiant energy is located at 480nm, which is the band. visible blue light. So the sky we see is blue, and the sea water is also blue.
The 200nm frequency band belongs to the ultraviolet category. Too much ultraviolet rays will be harmful to the human body, but most of the ultraviolet rays will be absorbed or reflected by the ozone layer as they pass through the atmosphere, and very few of them reach the ground. But our skin will still be damaged by prolonged exposure to the sun.
The stars in the universe are all undergoing nuclear fusion and are constantly emitting gamma rays; There are also supernova explosions and collisions of massive and small objects like neutron stars, which will produce more gamma rays and even gamma-ray bursts. Therefore, in space there are extremely many gamma rays. But these gamma rays are blocked by the atmosphere, and very few of them reach the surface of the Earth.
If you operate in the outer atmosphere, you are very susceptible to gamma rays and other cosmic rays, so astronauts must always wear modern space suits when stepping outside. The universe. But gamma rays are difficult to block. Astronauts operating in space or on extraterrestrial planets, although they have spacecraft and spacesuits for better protection, they still receive a large amount of radiation in reality. much more than the surface of the Earth.
Gamma rays have extremely strong penetrating power, only special materials with high density, such as lead plates, can have a certain blocking effect. Moreover, according to the intensity of the gamma rays, the thickness of the lead plate also needs to be increased.
Using gamma rays to benefit society
Human civilization is increasingly improved by the constant understanding of the laws of nature. Gamma rays themselves are a natural phenomenon and are a form of energy released by particles during aggregation or separation.
Any field of science can be used to benefit people or used to harm people. The same is true of gamma rays, which can either kill or benefit people.
Gamma rays are mainly used in industrial flaw detection and healthcare. Industrial flaw detection actually uses the penetrating power of gamma rays to check if there is any problem with the internal structure of industrial products.
In medical treatment, gamma knife and radiation therapy are commonly used. X-rays also play a large role in medical treatment, but are mainly used for imaging tests of people to see the condition inside the human body. The energy of gamma rays is much greater than X-rays, which can destroy lesions on the body through the surface of the human body, thereby destroying cancer cells and tumors in the body without leaving trauma, can reduce the harm to the human body, and can also touch surgical trauma.
Humans can now also produce high-energy gamma rays
Now, humans not only benefit from natural gamma rays, but scientists also produce high-energy gamma rays. In September 2011, a research team from the University of Strathclyde, UK discovered that ultra-short laser pulses can react with ionized gases to create an intense laser beam.
The laser beam that the team obtained is 1 trillion times brighter than the sun and can penetrate a 20cm thick lead sheet, and only a 1.5 meter thick concrete wall can completely shield it.
The most visible light in the sun’s electromagnetic spectrum is in the 480nm band, while this wavelength is 1 trillion times shorter, which is 4.8 x 10^-21m. The corresponding frequency of that short wavelength electromagnetic wave is 6.25 x 10^28Hz, and this is certainly an intense gamma beam.
This innovative discovery is significant and has the potential to be used in many areas in the future, such as better medical imaging, radiotherapy, and more widely in scientific experiments and industry. However, its lifetime is only 10 milliseconds, which is fast enough to record the nuclear response to stimulus, so it could facilitate further nuclear research.
Therefore, it can be concluded that mankind has understood and mastered the principle of gamma rays, and has long begun to use this law of nature to benefit humans.