Which processes occur within fractions of a second?

The correct answer encompasses all the processes listed, highlighting that all of them can occur in fractions of a second.

Absorption of radiation energy happens almost instantaneously when radiation is directed toward matter, as photons collide with atoms. This process can lead to immediate changes at the atomic level, which is crucial for understanding how radiation interacts with biological tissues.

Following absorption, the formation of active radicals can occur in a very short time frame. When radiation energy is absorbed by a molecule, it can result in the breaking of chemical bonds, leading to the creation of free radicals. These highly reactive species can form within picoseconds to nanoseconds after radiation interaction, making them key players in radiation chemistry and biology.

Finally, biochemical changes within cells can also take place very rapidly. Once free radicals are formed, they can initiate various cellular reactions almost immediately, influencing cell signaling and potentially leading to damage or cellular responses.

Thus, the processes of absorption of radiation energy, formation of active radicals, and subsequent biochemical changes occur very quickly, often within fractions of a second, demonstrating the complexity and speed at which radiation can affect biological systems. This interconnectedness shows the importance of understanding these rapid processes in the context of radiographic techniques and their implications for health and safety.