| English | Photoelectric effect |
|---|---|
| Bahasa Melayu | Kesan fotoelektrik |
| 中文 | 光电效应 |
Definition
The emission of electrons from a metal surface when light of high enough frequency shines on it.
In exam terms
The photoelectric effect is the emission of electrons from a metal surface when light of high enough frequency shines on it. The emitted electrons are called photoelectrons.
It is explained by the photon model: each photon gives all its energy hf to one electron.
Einstein's equation is hf = W + KE(max), where W is the work function and KE(max) is the maximum kinetic energy of the photoelectron, all in joules (J). A correct exam sentence: Electrons are emitted only when the light frequency is at least the threshold frequency, no matter how bright the light is.
Do not confuse it with…
Do not confuse the photoelectric effect with thermionic emission. In the photoelectric effect, electrons are released by absorbing photons of light; in thermionic emission, electrons are released by heating a metal.
One depends on light frequency, the other on temperature.
In Paper 2 this is asked as state what the photoelectric effect is, or explain why increasing brightness alone cannot cause emission below the threshold frequency. Stress that one electron absorbs one photon, so it is the energy hf of each photon, not the number of photons, that decides emission.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)