What are photons described as?

Photons are described as particles of light, which is a fundamental concept in physics and optics. Photons are the quantum units or "quanta" of electromagnetic radiation, meaning they are the smallest discrete amount of electromagnetic energy. Unlike traditional particles with mass, photons are massless and travel at the speed of light in a vacuum.

This characterization as particles of light highlights their dual nature as both particles and waves, which is central to the field of quantum mechanics. Light behaves as waves (exhibiting phenomena such as interference and diffraction), but can also be thought of as consisting of individual photons, making the particle description relevant and essential for understanding various processes in optics, including how lasers operate and how light interacts with matter.

In contrast, the other options do not accurately describe photons. Waves of sound pertain to mechanical vibrations in a medium, electrons in motion refers to charged particles, and molecules of heat do not exist in the context of electromagnetic radiation. This distinction allows for a clearer understanding of the behavior and properties of light in scientific applications.