| English | Photon |
|---|---|
| Bahasa Melayu | Foton |
| 中文 | 光子 |
Definition
A single quantum, or particle, of light or other electromagnetic radiation, carrying energy E = hf.
In exam terms
A photon is a single quantum, or particle, of light or other electromagnetic radiation. Each photon carries a fixed amount of energy given by E = hf, where h is Planck's constant (6.63 × 10⁻³⁴ J s) and f is the frequency in hertz (Hz), giving E in joules (J).
Because energy can also be written E = hc/λ, higher frequency (shorter wavelength) photons carry more energy. A correct exam line: E = hf = (6.63 × 10⁻³⁴ J s)(5.0 × 10¹⁴ Hz) = 3.3 × 10⁻¹⁹ J. The photon model explains the photoelectric effect, where each electron absorbs one photon.
Do not confuse it with…
Do not confuse a photon with an electron. A photon is a particle of light with no rest mass and no charge, carrying energy hf; an electron is a particle of matter with mass and a negative charge.
In the photoelectric effect a photon is absorbed and an electron is emitted, they are different objects.
In Paper 2 this is asked as state what a photon is, or calculate photon energy using E = hf. Always keep frequency in Hz and give the energy in J. If wavelength is given, first find f = c/λ before using E = hf.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)