The penetrating power of infrared rays depends on the wavelength of the radiation. Longer wavelength infrared rays, such as those emitted by thermal sources like human skin or the sun, have lower energy and can penetrate the skin and other materials to some extent. These rays are commonly used in applications like thermal imaging, where they can reveal the temperature distribution of objects.

Mid-wavelength infrared radiation, also known as mid-IR, has intermediate energy and can penetrate certain materials, including some plastics, glass, and organic solvents. These rays find applications in various fields, such as spectroscopy and medical imaging.

In contrast, short wavelength infrared rays or far-infrared rays have higher energy and stronger penetrating power. They can pass through many materials, including metals, semiconductors, and most non-metallic substances. These high-energy infrared rays are commonly used in security and military applications, such as night vision and thermal imaging systems, as well as in industrial processes like material analysis and non-destructive testing.

However, it's worth noting that the penetrating power of infrared rays is still limited compared to other types of electromagnetic radiation like X-rays or gamma rays. Infrared rays can be absorbed, reflected, or scattered by various materials, and their penetration depth depends on factors such as the wavelength, the material's composition and density, and the thickness of the material.