Wave speed

The speed, or velocity, of a wave can be calculated using the equation:

wave speed = frequency × wavelength

v = f\lambda

This is when:

  • wave speed (v) is measured in metres per second (m/s)
  • frequency (f) is measured in hertz (Hz)
  • wavelength (λ) is measured in metres (m)

Example calculation

What is the speed of a sound wave that has a frequency of 50 Hz and a wavelength of 6 m?

wave speed = frequency × wavelength

wave speed = 50 × 6

wave speed = 300 m/s

Question

What is the speed of a water wave with a frequency of 0.2 Hz and a wavelength of 25 m?

wave speed = frequency × wavelength

wave speed = 0.2 × 25

wave speed = 5 m/s

Question

What is the wavelength of a radio wave with a frequency of 990 kHz and speed of 300,000,000 m/s?

wave speed = frequency × wavelength

990 kHz = 990,000 Hz

wavelength = \frac{wave~speed}{frequency}

wavelength = \frac{300,000,000}{990,000} = 303~m