5.1 Properties of Waves

• Waves are generated by oscillating sources 
  • These oscillations travel away from the source

• Oscillations can propagate through a medium (e.g. air, water) or in a vacuum (i.e. no particles), depending on the wave type

Wave Features

• In order to describe the properties of travelling waves, the following keywords need to be defined:
  • Wavelength λ (m) is the distance between a point on a wave and the same point on the next cycle of the wave, e.g. two crests, or two troughs
  • Amplitude A (m) is the magnitude of the maximum displacement reached by an oscillation in the wave 
  • Period T (s) is the time taken for one complete oscillation at one point on the wave
  • Frequency f (Hz) is the number of complete wave cycles per second 
  • Wave speed c (m s^-1) is the rate of movement of the wave

Diagram showing the amplitude and wavelength of a transverse wave

• The frequency f and the period T of a travelling wave are related to each other by the equation

(i) Identify the amplitude A of the wave on the graph 

• • The amplitude is defined as the maximum displacement from the equilibrium position (x = 0)

• • The amplitude must be converted from centimetres (cm) into metres (m)

A = 0.1 m

(ii) Calculate the frequency of the wave

Step 1: Identify the period T of the wave on the graph 

• • The period is defined as the time taken for one complete oscillation to occur

• • The period must be converted from milliseconds (ms) into seconds (s)

T = 1 × 10^–3 s

Step 2: Write down the relationship between the frequency f and the period T 

f = 

Step 3: Substitute the value of the period determined in Step 1

f = 

f = 1000 Hz