When a photon traverses a medium, which of the following events can occur?

When a photon traverses a medium, multiple interactions can occur, making the option that includes no interaction, complete absorption, or scattering the correct choice.

Photons can pass through a medium without interacting, which means they continue on their path without losing energy. This is known as 'no interaction.' In many materials, especially those with low atomic number and density, the likelihood of this occurring is significant, particularly for high-energy photons such as gamma rays.

Complete absorption involves the photon transferring all of its energy to the medium, usually resulting in ionization of the atoms or molecules in that medium. This event is significant in medical applications like radiation therapy, where the goal may be to absorb the maximum dose within a tumor.

Scattering occurs when a photon interacts with an electron or nucleus in the medium and changes direction without being absorbed. This can include coherent scattering, where the photon retains its energy, or Compton scattering, where it transfers some of its energy to an electron and continues moving in a different direction.

Therefore, the option encapsulating these three potential events accurately reflects the physics of photon interactions with matter, making it the most comprehensive and correct answer.