using waves

• Sound waves travel through a solid by the particles in the solid vibrating and transferring kinetic energy through the material
• The human ear works in the following steps:

  • The outer ear collects the sound which travels into the ear
  • The sound waves cause the eardrum to vibrate at the same frequency
  • This is amplified by three ossicles (small bones)
  • This causes the hair in the cochlea to vibrate
  • The cochlea converts the vibrations into electrical signals
  • The signals are passed to the brain through the auditory nerve
  • The brain converts the electrical signals into sound
• The frequency range of human hearing is 20 Hz - 20kHz (1kHz = 1000 Hz)
• An ultrasound wave is a sound wave with a frequency greater than 20,000 Hz
• Sound of frequencies less than 20Hz is called Infrasound
• Seismic waves are produced by earthquakes and they produce both P-waves and S-waves
• P waves are longitudinal waves
• S waves are transverse waves
• A difference between the mediums that P-waves and S-waves can travel through is:

  • P-waves travel through both solids and liquids
  • S-waves only travel through solids (not liquids)
• The significance of P and S waves is that they provide evidence that the Earth has a liquid core; only P waves produced by an earthquake can be detected on the other side of the globe
• Echo sounding is a technique used to detect objects in deep water and measure water depth by emitting, reflecting, and detecting high frequency sound waves, then calculating distances using the time difference between emission and detection, alongside wave speed
• Sonar works by emitting ultrasound waves that reflect off boundaries and their echoes are detected, then using the known speed of ultrasound and the time it takes to detect the echoes to calculate the distance travelled, halving it to find the distance between emitter and boundary
• Foetal scanning works by sending an ultrasound wave into the patient's body, which passes through and reflects off organs and tissue, then using the reflected ultrasound waves to produce an image of the foetus, without damaging cells as ultrasound is safe