# Wave speed equation

Wave speed = frequency x wavelength (v = f x lambda), measured in m/s.

Physics (school) · Part 05: Waves, sound and light · Card 3 of 8 · Last updated 2026-10-19

## Analogy

If 4 people pass a gate each second and each is 2 m long, the line moves at 8 m/s.

## Example

**Water waves**

f = 5 Hz
wavelength = 0.2 m
v = 5 x 0.2
v = 1 m/s

## In practice

Used to find the wavelength of a radio station or the speed of ripples in a tank.

## Practice

### Flashcards

- **What is the wave speed equation?** Wave speed = frequency x wavelength.

### Interview questions

**A water wave has a frequency of 4 Hz and a wavelength of 0.5 m. Calculate its speed and say how far it travels in 10 s.**

- v = f x wavelength = 4 x 0.5 = 2 m/s
- Distance = speed x time = 2 x 10
- Distance = 20 m

## Questions people ask

### How do I use v = f x wavelength?

Put frequency in hertz and wavelength in metres, then multiply to get speed in m/s. To find wavelength, divide speed by frequency. A wave with speed 340 m/s and frequency 170 Hz has a wavelength of 340 / 170 = 2 m.

### If frequency increases, what happens to wavelength?

In a given material the wave speed is fixed. So if frequency goes up, wavelength must go down to keep v = f x wavelength true. High-pitched sounds have short wavelengths, and low-pitched sounds have long ones, even though both travel at about the same speed in air.

## Related concepts

- [Amplitude, wavelength and frequency](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-2)
- [Waves](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-1)
- [Reflection](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-4)
- [Refraction](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-5)

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