The Wave Equation (AQA GCSE Physics): Revision Notes

6.1.3 The Wave Equation

The Wave Equation

Measuring the Speed of Sound Waves in Air

1. Divide the distance travelled by the time taken for the second person to hear the sound.

Problems with the Experiment

• Every person has a different reaction time.
• It takes a fraction of a second between hearing the sound and stopping the timer.
• It takes a fraction of a second between seeing the cymbals and starting the timer.

Reducing Errors

• Have a large number of observers with timers.
• All results can be taken and anomalous ones should be discarded.
• Calculate a mean value.
• The longer the distance, the longer the time, making it easier to start and stop the timer at the correct times.

Waves

• Wavelength (λ)
  • The distance between the same points on two consecutive waves.
• Amplitude (y)
  • The distance from the equilibrium line to the maximum displacement (crest or trough).
• Frequency (f)
  • The number of waves that pass a single point per second.
• Period (T)
  • The time taken for a whole wave to completely pass a single point.

Diagram Explanation

• Wave Diagram
  • The diagram shows a wave with labelled wavelength (λ) and amplitude (y).
  • The distance from crest to crest (or trough to trough) represents the wavelength.
  • The height from the equilibrium line to the crest or trough represents the amplitude.

Relationships (Physics Only)

• Increase Frequency, Velocity Increases
  • When the frequency increases, the wave velocity increases.
• Wavelength Increases, Velocity Increases
  • An increase in wavelength leads to an increase in wave velocity.
• The period is Inversely Proportional to Frequency
  • As the period decreases, the frequency increases.
• Smaller Period, Higher Frequency, Greater Velocity
  • A smaller period corresponds to a smaller frequency and, consequently, a greater wave velocity.