Transmission of Sound Waves (AQA GCSE Physics)

• Sound waves are longitudinal waves
  • They transfer energy by the molecules vibrating and knocking into neighbouring molecules

• The more molecules that are present the faster the wave can transfer energy, therefore:
  • Sound waves travel fastest in solids
  • Sound waves travel slowest in gases

• When sound waves move from one medium to another, there will be changes to its:
  • Wave speed
  • Frequency
  • Wavelength

• The relationship between the wave speed, wavelength and frequency can be determined using the wave equation
• This change in velocity can also result in a change of direction of the sound wave
  • This phenomenon is also known as refraction

Refraction of Sound

• When sound moves from a denser medium to a less dense medium:
  • The wavelength of the sound wave decreases
  • The frequency of the sound wave stays the same
  • The velocity of the sound wave decreases
    

• When sound moves from a less dense medium to a denser medium:
  • The wavelength of the sound wave increases
  • The frequency of the sound wave stays the same
  • The velocity of the sound wave also increases

• The speed of sound in air is also affected by temperature
  • On warm days, air molecules move faster, hence they carry sound waves faster, increasing the speed of sound
  • On cold days, air molecules move at a slower pace, so they carry sound waves at a slower pace, decreasing the speed of sound