What determines the penetrating power of X-rays?

The penetrating power of X-rays is primarily determined by the energies and frequencies of the X-rays. Higher energy X-rays have shorter wavelengths and greater frequencies, which allow them to penetrate materials more effectively. This is because higher-energy photons can interact with the atomic structure of matter in such a way that they can pass through with less absorption or scattering.

X-ray photons behave similarly to other forms of electromagnetic radiation, where increased energy translates to increased ability to overcome the forces that keep atoms together. As such, X-rays with higher frequencies can more effectively ionize atoms and disrupt their electronic structures, allowing them to pass through denser materials.

While factors like the contact time of X-rays with a material and the properties of the material itself do influence the overall interaction, the intrinsic properties of the X-rays themselves—specifically their energies and frequencies—are the main determinants of how deeply they can penetrate various substances.