While photons have no rest mass, they do possess energy and momentum. The interaction of photons with matter occurs through the electromagnetic force, which is responsible for interactions between charged particles. When a photon encounters matter, several processes can occur:
Absorption: The photon can be absorbed by an atom or molecule, transferring its energy to an electron within the material. This can result in the promotion of the electron to a higher energy level or the complete ejection of the electron, depending on the specific energy of the photon.
Scattering: Photons can scatter off the electrons within matter. This scattering can be elastic, where the photon's energy and direction change but its frequency remains the same, or inelastic, where the photon transfers some of its energy to the electron.
Transmission: In some cases, photons can pass through matter without being significantly absorbed or scattered. This occurs primarily in materials that are transparent or translucent to the specific energy range of the photons. The transparency of materials depends on the energy levels and structures of the atoms or molecules in the material.
The ability of photons to pass through objects depends on the nature of the material and the specific energy of the photons. For example, visible light photons can pass through certain transparent materials like glass, while they are absorbed or scattered by opaque materials like metal. X-rays and gamma rays, which have higher energies, can penetrate through a wider range of materials.
It's worth noting that even in cases of transmission, photons can still interact with matter to some extent. However, their ability to pass through objects without being absorbed or scattered depends on factors such as the energy of the photons, the density and composition of the material, and the specific interactions at the atomic or molecular level.