| English | Photoelectron |
|---|---|
| Bahasa Melayu | Fotoelektron |
| 中文 | 光电子 |
Definition
An electron emitted from a metal surface as a result of the photoelectric effect.
In exam terms
A photoelectron is an electron that is emitted from a metal surface when light of high enough frequency shines on it, the photoelectric effect. Each photon of energy E = hf gives its energy to one electron.
If hf is greater than the work function W, the electron escapes with maximum kinetic energy KE = hf − W, measured in joules (J). A photoelectron has the same charge (−1.6 × 10⁻¹⁹ C) and mass as any other electron.
Example of correct use: "When ultraviolet light struck the zinc plate, photoelectrons were emitted and the leaf of the electroscope fell." No emission happens below the threshold frequency, however bright the light.
Do not confuse it with…
Do not confuse a photoelectron with a photon. A photon is a packet of light energy (E = hf) that has no charge and no rest mass; a photoelectron is a real charged electron released after a photon is absorbed.
One photon frees at most one photoelectron.
In Paper 2, this is asked as define or explain, such as "What is a photoelectron?" or "Explain why no photoelectrons are emitted below the threshold frequency." A good answer links each photon to one electron and states that hf must be at least equal to the work function.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)