GCSEPhysicsOCR GatewayRevision Notes5. Waves in Matter5.1 Wave Behaviour5.1.2 The Wave Equation

The Wave Equation (OCR Gateway GCSE Physics)

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The Wave Equation

  • Wave speed is defined as:

The distance travelled by a wave each second

  • Wave speed is given the symbol ν and is measured in metres per second (m/s)
  • Wave speed is the speed at which energy is transferred through a medium
  • Transverse and longitudinal waves both obey the wave equation:

Wave equation, IGCSE & GCSE Physics revision notes

  • Where:
    • v = wave speed in metres per second (m/s)
    • f = frequency in Hertz (Hz)
    • λ = wavelength in metres (m)

  • The wave speed equation may need to be rearranged, which can be done using this formula triangle:

Wave speed triangle (2), IGCSE & GCSE Physics revision notes

Worked example

Using the Wave Equation

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

Part (a)

Step 1: List the known quantities

    • Time period, T = 2 s

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

Time Period Equation

Step 3: Rearrange for frequency, f, and calculate the answer

f = 1 ÷ T = 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 × λ

Step 3: Rearrange the equation to calculate the wavelength

λ = v ÷ f

Step 4: Use the frequency you calculated in part (a) and put the values into the equation

λ = 0.15 ÷ 0.5

Wavelength, λ = 0.30 m

Examiner Tip

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

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    Previous:5.1.1 Describing Wave MotionNext:5.1.3 Transverse & Longitudinal Waves
    Ashika

    Author: Ashika

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    Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.