A girl sits on a rock in the sea and watches the waves move past. She observes that five full wavelengths pass her in $20\,\text{s}$. Determine the frequency of this wave.
- A$0.25\,\text{Hz}$
- B$4.0\,\text{Hz}$
- C$15\,\text{Hz}$
- D$100\,\text{Hz}$
Physics 0625 · IGCSE · General properties of waves