Albert Teen
powered by
Albert logo


Speed of Wave

Speed of Wave

Speed of Wave

The speed of a wave is given by wavelength x frequency.

Waves are the transfer of energy. This transfer happens over a distance at a certain speed (v).

How do you calculate speed (v)?

The speed of a wave can be calculated with its frequency (f) and wavelength (λ). What is the frequency of a wave?

What is the SI unit for measuring the wavelength (λ)(\lambda) of a wave? 

What is the unit for speed (v)?

Now let's have a go at deriving the equation for the speed of a wave. We will do this, using wavelength and frequency.


We derived the SI unit for frequency from its equation. What is this? Remember Hertz is not the SI unit.


What is the SI unit for wavelength?


So, we know that the unit for speed is m/s^m/_s . This can also be written as m×1sm\times \frac{1}{s} . Notice these are the two units for wavelength and frequency. So which one of these options if the correct formula for speed of a wave?

A: speed=wavelengthfrequencyspeed = \frac{wavelength}{frequency}

B: speed=wavelength×frequencyspeed=wavelength \times frequency

Answer A or B.

What is the equation for speed? Given that wavelength (λ) is measured in metres (m)(m) , frequency (f) is measured in Hertz or 1s\frac{1}{s} , and speed (v) is measured in m/s^m/_s .

So the speed of a wave is given by v=f×λv=f\times\lambda where v is speed, f is frequency, and λ is wavelength.

What is the speed of a wave that has a frequency of 20 Hz and a wavelength of 250m?

The speed of sound in air is 343m/s343m/_s What is the wavelength of a sound wave with a frequency of 49Hz49Hz ?

What is the frequency of red light, that has a wavelength of 700nm700 nm ? The speed of light is always 300,000,000m/s300,000,000m/_s or 3×108m/s3\times10^8m/_s .

The speed of a wave depends on the medium the wave is travelling through. We will look at this more closely in later lessons.