Waves

• What do waves do

  waves transfer energy and information without transferring matter
• what is frequency of a wave 


  measured in Hertz (Hz) the number of waves passing a point each second
• what is wavelength 


  the distance between two points on a wave that are in phase with eachother
• what is the amplitude of a wave

   maximum disturbance from its undisturbed position.
• what is the period of a wave


  time taken for the wavelength to pass one point

  equation = 1/frequency
• what is a longitudinal wave

  sound waves and seismic P waves are examples of longitudinal waves

  particles in longitudinal waves are parallel to the direction of the wave
• what are transverse waves

  water waves and seismic S waves are examples of longitudinal waves . particles are perpendicular to the direction of the wave
• what is the equation for wave speed

  wave speed = frequency × wavelength

  v = f ×λ

  wave speed (metre/second, m/s) = distance (metre, m) ÷ time (second, s)
• Describe how to measure the velocity of sound in air

  measure distance from sound source to wall

  measure the time interval , with a stopwatch , from the sound being produced and the echo being heard

  use : speed = distance / time to calculate the speed of sound in air

  repeating this multiple times at a range of distances will allow u to obtain precise results
• what happens to a sound wave when densities are similar 


  sound is transmitted through a material
• what happens to sound waves when there is a big difference in densities

  the sound is reflected
• what is refraction

  refraction can result when there is a change in both speed and direction . the direction does not change if the wavefronts are perpendicular to the normal
• What range of frequencies can the human ear hear

  20Hz-20,000Hz
• How do sound waves travel in the ear

  air molecules rare forced to vibrate by the source of the vibration

  energy travels via longitudinal waves until it reaches the ear
• What do u call sound below frequencies of 20Hz and 20KHz

  <20Hz = infrasound

  >20,000Hz = ultrasound
• how does the ear detect sound

  sound waves are channelled down the ear canal and cause the eardrum to vibrate . These vibrations pass through the ear as further vibrations and then convert to an electrical signal and carried to the brain
• How can infrasound waves be used

  infrasound waves can be detected from explosions under the ground . The infrasound waves can also help determine the structure of rocks between the earths crust
• explain how ultrasound is used in prenatal scans 


  ultrasound waves are used to make images inside the body

  they are not harmful so are safe to use on a foetus

  the ultrasound waves are sent into the womans body and some of the sound is reflected each time it meets a layer of tissue with a different density to the one it has just passed through

  the scanner detects echoes and a computer uses the information to make an image
• explain how ultrasound is used in sonar

  pulses of ultrasound are used to find the depth of water beneath a ship . the sonar equipment measures the time between sending the sound and detecting the echo . The time is used to calculate the depth of the water using the equation : distance = speed x time , but because depth is half the distance the sound has travelled u have to half your answer to find the depth