X-rays are electromagnetic waves with short wavelengths, or a stream of photons with high energy. X-ray intensity refers to the radiant energy passing through a unit area perpendicular to the ray per unit time. X-ray intensity can be changed by changing tube current or tube voltage. Increasing the tube current can increase the number of electrons hitting the anode target per unit time, so the intensity of X-rays can be increased; increasing the tube voltage can increase the energy (E = eu) obtained by the electrons in the electric field, resulting in Photon energy also increases, so X-ray intensity can also be increased. In application, the X-ray intensity is usually changed by adjusting the tube current at a certain tube voltage, so the tube current (mA) is commonly used in medicine to reflect its intensity.