The interaction of light with matter depends on the properties of both the light and the object it encounters. In the case of infrared (IR) light, it can penetrate certain objects that block visible light due to the differences in their wavelengths and how they interact with matter.
When light interacts with an object, several processes can occur: absorption, transmission, reflection, and scattering. The behavior of light in these processes depends on the energy (or wavelength) of the photons and the characteristics of the object's materials.
Visible light has shorter wavelengths and higher energy compared to infrared light. Objects that appear opaque to visible light typically absorb and scatter those photons, preventing their transmission through the object. The atoms or molecules in the material absorb the energy of the visible photons, leading to electronic transitions or vibrations within the material. These absorbed photons are then re-emitted or converted into other forms of energy, such as heat.
Infrared light, on the other hand, has longer wavelengths and lower energy compared to visible light. Some materials that may appear opaque to visible light can be partially transparent or transparent to infrared light. This occurs because the energy of infrared photons is generally lower than the energy required for electronic transitions in most materials. Instead, the interaction of infrared light with matter primarily involves the excitation and vibration of molecular bonds.
Infrared light can penetrate certain materials because the atoms and molecules in those materials do not efficiently absorb or interact with photons in the infrared wavelength range. Instead, the photons may pass through the material relatively unaffected, leading to transmission. However, it's important to note that not all materials are transparent to infrared light, and the extent of transmission depends on the specific properties of the material and the wavelength range of the infrared light.
Regarding infrared heat, it is essentially the transfer of thermal energy in the form of infrared radiation. Heat transfer occurs when an object at a higher temperature emits infrared radiation, and this radiation can be absorbed by another object at a lower temperature. Infrared heat, like infrared light, can penetrate certain materials that block visible light. The ability of infrared heat to pass through objects depends on the material's transparency to infrared radiation and the wavelengths involved.
In summary, infrared light can penetrate some objects that block visible light due to the differences in their wavelengths and the way they interact with matter. While visible light is absorbed and scattered by certain materials, infrared light has longer wavelengths and lower energy, allowing it to pass through or be partially transmitted. Infrared heat, as a form of thermal energy carried by infrared radiation, can similarly penetrate materials that are transparent or partially transparent to infrared wavelengths.