The Wave Equation (Edexcel GCSE Combined Science: Physics): Revision Note

A wave in a pond has a speed of 0.15 m/s and a time period of 2 seconds. Calculate:

a) The frequency of the wave

b) The wavelength of the wave

Answer:

Part (a)

Step 1: List the known quantities

• Time period, T = 2 s

Step 2: Write out the equation relating time period and frequency

$T=\frac{1}{f}$

Step 3: Rearrange for frequency f and calculate the answer

$f=\frac{1}{T}=\frac{1}{2}$

Frequency, f = 0.5 Hz

Part (b)

Step 1: List the known quantities

• Wave speed, v = 0.15 m/s

• Frequency, f = 0.5 Hz

Step 2: Write out the wave speed equation

$v=f\times \lambda$

Step 3: Rearrange for wavelength λ and calculate the answer

$\lambda =\frac{v}{f}=\frac{0.15}{0.5}$

Wavelength, λ = 0.30 m

When stating equations make sure you use the right letters:

For example, use λ for wavelength, not L or W

If you can’t remember the correct letters, then just state the word equations

Be careful with units: wavelength is usually measured in metres and speed in m/s, but if the wavelength is given in cm you might have to give the speed in cm/s

Likewise, watch out for frequency given in kHz: 1 kHz = 1000 Hz