Photoelectron

Part of speech: noun

Definitions

1. A negatively charged particle ejected from an atom when it absorbs light energy
2. An elementary particle released from a material due to the photoelectric effect when light strikes it
3. A quantum of electrical charge derived from the outer shell of an atom as a result of light exposure

Etymology: Photoelectron is a compound built from two Greek-derived parts, and its first half is itself a word that once meant something quite different. "Photo-" comes from Greek "phōs," meaning light, while "electron" comes from Greek "ēlektron," the word for amber, the yellowish fossil resin that produces a static charge when rubbed. The link between amber and electricity is what gave the second half its modern sense: early experimenters noticed that rubbed amber attracted light objects, and the Greek name for amber became the root of the words for electrical phenomena. Combining the two produces a word for an electron released from a surface by light, a process in which light strikes a material and knocks loose charged particles. The "electron" in it carries the electrical sense, while "photo-" signals that light is the trigger. The second element is therefore a survival of the amber root, now attached to the modern physics of the atom.