What describes gamma rays?

Gamma rays are best described as electromagnetic waves emitted from the nucleus of an atom. They are a form of high-energy radiation that occurs during nuclear reactions, such as radioactive decay. Unlike particles, which have mass and a charge, gamma rays are photon-based and thus have no mass or charge. Their high frequency and short wavelength classify them within the electromagnetic spectrum, alongside other types of radiation like X-rays and visible light.

The other descriptions provided pertain to different types of particles or radiation. For instance, helium nuclei reference alpha particles, which are made up of two protons and two neutrons and do have mass. High-energy particles with a positive charge highlight beta particles or alpha particles, neither of which are gamma rays. The mention of infrared light pertains to lower energy electromagnetic radiation typically associated with thermal radiation, not the high-energy emissions from atomic nuclei seen with gamma rays.