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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 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
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