| English | Wave speed |
|---|---|
| Bahasa Melayu | Laju gelombang |
| 中文 | 波速 |
Definition
The distance travelled by a wave in one second, equal to frequency multiplied by wavelength (v = fλ).
In exam terms
Wave speed is the distance travelled by a wave in one second. Its symbol is v and its unit is the metre per second (m s⁻¹).
It is given by the wave equation v = fλ, where f is the frequency in Hz and λ is the wavelength in m. For example, a water wave of frequency 4 Hz and wavelength 0.5 m has speed v = fλ = 4 Hz × 0.5 m = 2 m s⁻¹.
Wave speed depends on the medium: sound travels faster in water than in air, and light travels fastest in a vacuum.
Do not confuse it with frequency
Wave speed is how fast the wave profile moves through a medium (m s⁻¹), while frequency is how many waves are made each second (Hz). Changing the source frequency does not change the speed in a given medium; instead the wavelength adjusts so that v = fλ still holds.
In Paper 2 you are usually asked to calculate wave speed with v = fλ, or to explain why speed changes when a wave enters a new medium. Keep frequency in Hz and wavelength in metres so the answer comes out in m s⁻¹.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)