But it can kill cells, so it can also be used to kill cancer cells for medical purposes.
In 1900, French scientist P.V. Villard (Paul Ulrich Villard) discovered that barium chloride containing radium was passed through cathode rays, and from the photographic record, the radiation was seen to pass through 0.2 millimeters of lead foil, and La Seyffe called this very strong penetrating radiation gamma rays, which are the third type of nuclear rays discovered after alpha and beta rays.
1. γ-rays Electromagnetic waves with a wavelength shorter than 0.2?. Produced by radioactive isotopes such as 60Co or 137Cs. It is a high-energy electromagnetic wave with a short wavelength (0.001-0.0001nm), strong penetration, long range, and can irradiate a lot of material at a time, and the dose is relatively uniform, dangerous, and must be shielded (a few cm of lead plate or a few meters thick concrete wall).
2. X-rays Wavelength between ultraviolet and γ-rays between the electromagnetic radiation. Discovered by the German physicist W.K. Roentgen in 1895, so also known as Roentgen rays. Is produced by the x-ray machine high-energy electromagnetic waves. The wavelength is longer than γ-rays, the range is slightly closer, and the penetrating power is not as good as γ-rays. There is a danger that should be shielded (a few millimeters of lead plate).
3. β-rays from radioactive isotopes (such as 32P, 35S, etc.) released when the decay of negatively charged particles. Short range in the air, weak penetration. Ionization in living organisms than γ-rays, x-rays strong. β-rays are high-speed movement of the electron flow 0/-1e, penetration ability is very strong, ionization effect is weak, originally there is no left and right in the physical world, but β-rays are divided into left and right. In the process of beta decay, the radioactive nucleus is transformed into another kind of nucleus by emitting electrons and neutrinos, and the electrons in the product are called beta particles. In positive beta decay, a proton in the nucleus into a neutron, while releasing a positron, in the "negative beta decay", a neutron in the nucleus into a proton, while releasing an electron, that is, beta particles.
4. neutron A stream of uncharged particles. The source of radiation is a nuclear reactor, gas pedal or neutron generator, which produces a nuclear reaction when the nucleus of an atom is bombarded by foreign particles, which are released from the nucleus. Neutrons are categorized by their energy: fast neutrons, slow neutrons, and thermal neutrons. Neutrons have a high ionization density and often cause large mutations. Currently in radiation breeding, the application of more thermal neutrons and fast neutrons.
5. Ultraviolet light, or UV light, is a non-ionizing radiation with very weak penetrating power. Nucleic acids absorb the energy of UV light at a certain wavelength and are in an excited state, causing organic compounds to intensify their activity and thus causing mutations. It can be used to treat microorganisms and pollen grains of plants.
6. Laser A new light source developed in the 1960s.
Laser is also an electromagnetic wave. The wavelength is long and the energy is low. Because it is a good direction, only about 0.1 ° deviation, high brightness per unit area, monochromatic, can make biological cells *** vibration absorption, resulting in atoms, molecules, energy state excitation or atomic, molecular ionization, thus causing internal mutations in the organism.
Various rays, due to different ionization density, the biological effect is different, the mutation rate caused by the difference. In order to obtain a higher favorable mutation, it is necessary to choose the appropriate rays, but due to the ray source, equipment conditions and safety factors, the most commonly used are γ-rays and x-rays. Visible light, infrared light, ultraviolet light, etc., are caused by originating from the outer electrons. R?ntgen rays are caused by the inner layer of electrons. gamma rays are caused by the nucleus.