What is the principle of X-ray?

The basic principle of X-ray imaging, the reason why X-rays can make human tissues form images on the screen or film is based on the penetrability, fluorescence effect and photosensitive effect of X-rays. On the other hand, it is based on the difference in density and thickness between human tissues. When X-rays pass through different tissues and structures of human body, the absorption degree is different, so the amount of X-rays reaching the screen or film is also different. In this way, images with different light and dark or black and white contrast are formed on the screen or X-ray film.

X-ray (English: X-ray), also known as X-ray, X-ray, Roentgen ray or X-ray, is an X-ray with a wavelength range of 0.0 1 nm to 10 nm (corresponding to a frequency range of 30? PHz to 30EHz). X-ray was originally used in medical image diagnosis and X-ray crystallography. X-ray is also a kind of radiation harmful to human body, such as ionizing radiation. The x-ray wavelength range of human lung overlaps with gamma rays in a short place.

Extended data:

X-ray generation

X-ray wavelength is slightly greater than 0.5? Nanometer is called soft X-ray. The wavelength is less than 0. 1? Nanometer is called hard x-ray. Hard X-rays overlap with long-wavelength (low-energy) gamma rays, and the difference between them lies in the radiation source, not the wavelength: X-ray photons are accelerated by high-energy electrons, while gamma rays are produced by nuclear decay.

The simplest way to generate X-rays is to hit a metal target with accelerated electrons. In the process of impact, electrons will suddenly decelerate, and their lost kinetic energy will be released in the form of photons, forming a continuous part of the X-ray spectrum, which is called braking radiation. By increasing the accelerating voltage, the energy carried by electrons increases, which may knock out the internal electrons of metal atoms. So the inner layer forms a hole, and the outer layer electrons jump back to the inner layer to fill the hole, and at the same time emit photons with a wavelength of about 0. 1 nm. Because the energy released by the outer electron transition is quantized, the wavelength of the released photons is also concentrated in some parts, forming characteristic lines in the X-ray spectrum, which is called characteristic radiation.

In addition, high-intensity X-rays can also be generated by synchrotron or free electron laser. Synchrotron radiation source has the characteristics of high intensity, continuous wavelength, beam collimation, extremely small beam cross-sectional area, time pulse and polarization, and has become the best X-ray source for scientific research.

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