How to distinguish hard x-rays from soft x-rays?

Electromagnetic radiation with a wavelength between ultraviolet and gamma rays. It was discovered by German physicist W.K. Roentgen in 1895, so it is also called Roentgen ray. Ultra-hard x-rays with wavelength less than 0. 1 angstrom, hard x-rays with range of 0. 1 ~ 1 angstrom, and soft x-rays with range of1~1angstrom. X-rays are produced by X-ray tubes in the laboratory. X-ray tube is a vacuum tube with cathode and anode. The cathode is made of tungsten wire, which can emit hot electrons when energized, and the anode (called target electrode) is made of high melting point metal (generally tungsten, and the X-ray tube used for crystal structure analysis can also be made of iron, copper, nickel and other materials). Electrons are accelerated by high voltage of tens of thousands of volts to hundreds of thousands of volts, and the electron beam bombards the target electrode, emitting X-rays from the target electrode. When electrons bombard the target, it will produce high temperature, so it is necessary to cool the target with water, and sometimes the target is designed to rotate. X-ray spectrum consists of continuous spectrum and labeled spectrum. The marker spectra overlap on the background of continuous spectra. Continuous spectrum is bremsstrahlung caused by high-speed electrons being blocked by the target, and its short-wave limit λ 0 is determined by accelerating voltage V: λ 0 = hc /( ev) is Planck constant, e is electron quantity, and c is the speed of light in vacuum. The identification spectrum consists of a series of linear spectra, which are produced by the transition of electrons in the inner layer of the target element. Each element has a specific set of identification spectra, which reflects the characteristics of atomic shell structure. Synchrotron radiation source can produce high-intensity continuous spectrum X-rays and has become an important X-ray source. The role of X-ray X-ray has a strong penetrating power, which is often used in perspective inspection in medicine and flaw detection in industry. Long-term exposure to X-ray radiation is harmful to human body. X-ray can excite fluorescence, ionize gas and make photosensitive latex sensitive, so X-ray can be detected by ionization meter, scintillation counter and photosensitive latex sheet. Crystal lattice structure can produce significant diffraction effect on X-ray, and X-ray diffraction method has become an important means to study crystal structure, morphology and various defects. X-ray discovery1895165438+1October 8th is a Friday. In the evening, the whole campus of Wü rzburg University in Munich, Germany was immersed in a quiet atmosphere, and everyone went home for the weekend. But there's another room with a light on. Under the light, a scholar over 500 years old is staring at a pile of gray-black photographic negatives in a daze, as if lost in thought ... what is he thinking? It turns out that this scholar has done discharge experiments before. In order to ensure the accuracy of the experiment, he wrapped all kinds of experimental equipment with tin foil and cardboard in advance, and used cathode tubes without aluminum windows to let cathode rays pass through. But now, he was surprised to find that a screen coated with barium cyanoplatinum emitted by cathode rays (this screen was used in another experiment) gave off light. And the pile of negatives that were tightly closed next to the discharge tube has now turned gray-black-this shows that they have been exposed! This phenomenon that ordinary people will soon ignore has attracted the attention of this scholar and aroused his strong interest. He thought: the change of the negative film just shows that the discharge tube has released a new kind of penetrating ray, which can even penetrate the bag containing the negative film! Be sure to study it carefully. However-because we don't know what it is, we named it "X-ray". So the scholar began to study this mysterious X-ray. He first put a screen coated with fluorescent powder near the discharge tube and found that the screen immediately glowed. Then, he tried to take some opaque substances, such as books, rubber sheets and wooden boards, and put them between the discharge tube and the screen to block the invisible mysterious rays, but no one could stop them. There is almost no shadow on the screen, and you can even easily penetrate 15mm thick aluminum plate! It was not until he put a thick metal plate between the discharge tube and the screen that the shadow of the metal plate appeared on the screen-it seems that this ray still has no ability to penetrate too thick material. The experiment also found that only lead plate and platinum plate can make the screen non-luminous, and when the cathode tube is opened, the photosensitive film placed next to it will also be illuminated, even if it is wrapped with thick black paper. Then something even more amazing happened. One night Roentgen came home very late, and his wife came to see him in the laboratory, so his wife became the first person to leave traces on the photographic film under the action of unknown radiation. At that time, Roentgen asked his wife to cover the photographic film with her hand. After being developed, the couple saw images of phalanges and wedding rings on the negative. This discovery is of great value to medicine. It is like giving people a pair of "glasses" that can see things through the skin, so that doctors can "see" through human flesh and bones and clearly observe various physiological and pathological phenomena in the living body. According to this principle, people later invented the X-ray machine, and X-ray became an indispensable weapon in modern medicine. People accidentally fell, in order to check whether they broke, don't they all go to the hospital to "take a picture" first? This is taking pictures with X-rays! Although the scholar discovered X-ray, people at that time, including himself, didn't know what it was. It was not until the beginning of the 20th century that people realized that X-rays were actually electromagnetic waves shorter than light waves. It is not only widely used in medicine, but also a powerful weapon for human beings to overcome many diseases, and it also provides important evidence for major changes in physics in the future. It is for these reasons that this scholar became the first person in the world to win the Nobel Prize in physics at the Nobel Prize awarding ceremony in 190 1. To commemorate Roentgen, people named X-rays Roentgen rays.