Which effect is NOT caused by ionizing radiation?

The correct answer identifies that the creation of additional nuclei is not an effect caused by ionizing radiation. Ionizing radiation primarily interacts with matter by transferring energy that can lead to physical and chemical changes in atoms and molecules, typically resulting in damage at the cellular and molecular levels.

When ionizing radiation passes through a substance, such as biological tissue, it can break bonds within DNA strands, unbond base pairs, and cause cellular damage. These are direct consequences of the energy being released during interactions with atoms, leading to ionization or excitation of atoms and molecules, hence altering their structure or function.

Creating additional nuclei, however, pertains more to nuclear fusion or fission processes rather than biological interactions resulting from ionizing radiation. Ionizing radiation does not create new atomic nuclei but may cause reactions that can lead to changes in existing ones, such as through radioactive decay. This distinction clarifies why the creation of additional nuclei does not fall under the effects of ionizing radiation in biological systems.