Final answer:
Protection from ionizing radiation is most effective when combining distance from the source, shielding material, and reduced time of exposure.
Step-by-step explanation:
The most effective factor of protection from ionizing radiation is a combination of distance from the source, shielding material, and time of exposure. To minimize exposure to ionizing radiation, it is essential to keep the least possible time in the radiation environment, maintain as much distance from the source as possible, and employ effective shielding between yourself and the radiation source.
Lead, for example, is a particularly effective shielding material due to its high density and the fact that it has a high number of electrons, which readily absorb radiation energy. The principle that the intensity of radiation decreases with the square of the distance from the source also underscores the importance of distance in reducing exposure.