| English | Amplitude |
|---|---|
| Bahasa Melayu | Amplitud |
| 中文 | 振幅 |
Definition
The maximum displacement of a vibrating particle from its equilibrium position.
In exam terms
Amplitude is the maximum displacement of a vibrating particle from its equilibrium (rest) position. It is a distance, so for a water or spring wave it is measured in metres (m), and its symbol is A.
On a displacement-distance or displacement-time graph, the amplitude is the height of a crest above the middle line, not the full distance from crest to trough. Amplitude tells you how much energy a wave carries: the energy transferred is proportional to the square of the amplitude, so a wave with twice the amplitude carries four times the energy.
Example: a pendulum released from 5 cm swings with an amplitude of 5 cm.
Do not confuse it with wavelength
Amplitude and wavelength describe different directions on a wave graph. Amplitude is measured up and down from the middle line (perpendicular to the direction of travel); wavelength is measured along the wave, from one point to the next in-phase point.
A common mistake is reading the peak-to-peak height as the amplitude when that is actually twice the amplitude.
In Paper 2 you are usually asked to state what amplitude means, or to read the amplitude off a graph. Look for the word displacement on the vertical axis and give the value with its unit.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)