Transmission of Sound Waves (AQA GCSE Physics): Revision Note

Transmission of Sound Waves

• 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 their:

  • Wave speed

  • Wavelength

• The frequency of a sound wave does not change when it moves from one medium to another

• 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