What does attenuation refer to in radiation protection?

In the context of radiation protection, attenuation refers specifically to the reduction of photon energy as it interacts with matter. This means that as photons pass through any material, their energy decreases due to various interactions, such as scattering or absorption. This gradual loss of energy is essential in understanding how different materials can shield and protect against radiation.

The other options present misconceptions about attenuation. For instance, while complete absorption or blockage of radiation signifies that no radiation passes through, attenuation merely describes the decrease in energy rather than total absorption. Additionally, the changing direction of photons after striking an object relates to scattering, not attenuation itself. Thus, the accurate understanding of attenuation is the process of energy reduction, aligning with the second option.