The Wave Equation (Edexcel GCSE Physics: Combined Science)

• Wave speed is defined as:

The distance travelled by a wave each second

• The wave speed can be calculated in a similar way to calculating the speed of moving objects:

• Where:
  • v = wave speed in metres per second (m/s)
  • x = distance travelled by the wave in metres (m)
  • t = time taken in seconds (s)

• All waves obey the wave equation, which is another way to calculate the wave speed:

• 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:

Part (a)

Step 1: List the known quantities

• • Time period, T = 2 s

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

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