X-ray is a particle flow produced by the transition of electrons in atoms between two energy levels with great differences, and it is an electromagnetic wave with a wavelength between ultraviolet and gamma rays. Its wavelength is very short, from 0.0 1 to 100 angstrom. It was discovered by German physicist W.K. Roentgen in 1895, so it is also called Roentgen ray. Roentgen rays have strong penetrating ability, and can penetrate many substances that are opaque to visible light, such as ink paper and wood. This invisible ray can make many solid substances have visible fluorescence, make photographic negatives sensitive and ionize air. 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 of 1 ~ 100 angstrom. 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.
If it is a maternity X-ray, it will have a great impact on the fetus, which is more likely to cause embryonic disability, fetal malformation and brain dysplasia, and increase the risk of cancer in children. Especially in the early pregnancy, this period is a critical period for the development of embryonic organs, and embryos are extremely sensitive to various harmful factors. When the lower abdomen is exposed to X-rays within two weeks of conception, the fertilized egg may die. X-ray has a strong teratogenic effect on embryos within 6 ~ 12 weeks, and can also lead to embryo death when the deformity is serious. Receiving radiation in the early stage of fetal growth will hinder fetal growth. After the second trimester, most organs of the fetus have basically formed, and radiation injury rarely causes obvious appearance deformity. However, during this period, the reproductive system, teeth and central nervous system of the fetus are still developing, so the influence of X-rays may lead to mental retardation and other consequences.