Here's why:

* Radiation: This refers to energy that travels in the form of waves or particles. Examples include light, X-rays, gamma rays, and even heat.

* Medium: This is the material through which the radiation is passing. It could be air, water, metal, etc.

* Collision events: As the radiation travels through the medium, it interacts with the atoms and molecules of the medium. These interactions can involve scattering, absorption, or a combination of both.

* Fails to exit: When radiation is absorbed, it means that the energy of the radiation is transferred to the medium, and the radiation itself ceases to exist.

In simpler terms: The radiation hits the medium, gets "caught" by the atoms or molecules, and loses its energy in the process.