Can an X-ray machine recognize paper?

Answer

An X-ray (X-) radiation device measures the “density” of the object through which the radiation passes. Therefore, such image is typically displayed in black and white. Where it is white or light gray there is a lot of matter, where it is dark or black little matter (or vice versa when the image is viewed negatively). With such a device it is completely impossible to distinguish paper from other materials.

An alternative technique exists to use X-rays or X-rays. It turns out that the absorption of this radiation depends not only on the density of the matter, but also on the type of atoms in the matter. By illuminating with 2 or more different wavelengths (“colors”) of X-rays, one can estimate the relative composition of the material in its atoms.

This method is already being used when checking baggage at airports. see link.

This method (“color X-ray”) is also being investigated for medical applications. See link.

The method would make it possible to distinguish paper, which is rich in carbon, from other materials. However, not from wood and plastics, which contain approximately the same amount of carbon.