| English | Refraction of waves |
|---|---|
| Bahasa Melayu | Pembiasan gelombang |
| 中文 | 波的折射 |
Definition
The change in direction of a wave as it passes from one medium to another because of a change in its speed.
In exam terms
Refraction of waves is the change in direction of a wave as it passes from one medium to another because its speed changes. In a ripple tank this is shown by water waves slowing down as they move from deep to shallow water.
During refraction the frequency stays the same, but the speed and the wavelength both change. When a wave slows down, its wavelength becomes shorter (from v = fλ, if v falls and f is fixed, λ falls too).
If the wavefronts meet the boundary at an angle, the direction of travel bends towards the normal on entering the slower medium.
Do not confuse it with diffraction
Refraction is a change of direction caused by a change of speed when crossing into a new medium; the wavelength changes. Diffraction is the spreading of a wave through a gap or round an obstacle, and the wavelength does not change. If the wave stays in one medium and simply spreads out, that is diffraction, not refraction.
In Paper 2 you may be asked to explain why waves refract, or to draw refracted wavefronts in shallower water. Show the wavefronts closer together (shorter wavelength) and the direction bending, while keeping the frequency the same.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)