Not can not penetrate, but rays in the medium will be absorbed and weakened, when a certain energy of the ray through the same thickness of different media, a class of high-density materials such as lead plate so that the weakening of the degree of copper, iron and other materials is much larger than a sufficient thickness of the lead plate can be a certain strength of the rays blocked to a very low level, and iron plate, copper plate so that the same effect of the blocking, we need to increase the larger thickness, so It is customary to use lead as a protective isolation material for rays, and the introduction of a so-called "lead equivalent" concept, that is, the effect of a certain barrier rays equivalent to how many millimeters of thick lead barrier protection level.
The X-ray machine is the use of X-rays are absorbed by different tissues of the barrier and get a perspective image of the ah.