| English | Planck's constant |
|---|---|
| Bahasa Melayu | Pemalar Planck |
| 中文 | 普朗克常数 |
Definition
The fundamental constant h relating the energy of a photon to its frequency (E = hf), with a value of about 6.63 × 10⁻³⁴ J s.
In exam terms
Planck's constant is the fundamental constant h that links the energy of a photon to its frequency through E = hf. Its value is about 6.63 × 10⁻³⁴ J s, and its unit is the joule second (J s).
It is one of the most important constants in quantum physics.
Because h is so tiny, quantum effects are only noticeable for very small systems like atoms and photons. A correct exam use: h is the gradient of a graph of photon energy E against frequency f. In photoelectric experiments, h can be found from the gradient of the graph of maximum kinetic energy against frequency.
Do not confuse it with…
Do not confuse Planck's constant h with the photon energy E. Planck's constant is a fixed number (6.63 × 10⁻³⁴ J s) that never changes; photon energy E = hf changes with frequency. h is a constant of proportionality, not an energy.
In Paper 2 this is asked as state the value and unit of h, or determine h from the gradient of an energy–frequency graph. When reading it from a graph, remember the gradient equals h in units of J s, and never quote h without its unit.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)