What are the photons called that are transmitted through a medium without any interaction?

The photons that are transmitted through a medium without any interaction are referred to as primary photons. This term specifically denotes the initial photons that enter a medium and continue on their path without being absorbed or scattered. In the context of radiation physics and dosimetry, it is crucial to differentiate primary photons from others because they carry the energy from the source and interact with the tissues in a predictable manner.

In clinical settings, understanding the behavior of primary photons helps in accurately calculating dose distributions, optimizing treatment plans, and ensuring effective radiation therapy. This makes it essential for dosimetrists to identify these photons, as they are integral to determining how radiation will be delivered to tumors while minimizing exposure to surrounding healthy tissue.

In contrast, secondary photons are those that result from interactions such as scattering or absorption within the medium, while scattered photons are the result of deflection due to interactions with particles in the medium. Reflected photons refer to those that bounce off a surface rather than passing through it. Each of these types carries different implications for dosimetry calculations and patient safety.