CP4: waves

• what do waves transfer?

  Energy and information without transferring matter
• define frequency 


  the number of waves passing a point per second in hertz (Hz)
• define wavelength


  The distance from the crest of one wave to another
• what is amplitude and period on a wave?

  Shown on the image:

  
• What is a longitudinal wave?

  The particles vibrate in the same direction as the direction of travel.

  Sound waves.
• What is a transverse wave?


  Light, electromagnetic or water waves

  Has peaks and troughs.

  vibrates at a right angle to the direction of travel.
• Which form of seismic wave do longitudinal waves form?

  P-waves
• what form of seismic wave do transverse waves produce?

  S waves
• what is the equation for wave speed?

  wave speed (metre/second, m/s) = frequency (Hz) x wavelength (m)

  v = f x λ

  v= wave speed

  f= frequency

  λ= wavelength
• What is the equation relating wave speed, distance and time?


  wave speed (m/s) = distance (m)/ time (s)

  v = x/t

  v= wave speed

  x= distance

  t= time
• What happens when you increase velocity?

  Frequency increases and vice versa
• What happens when wavelength increases?

  Velocity increases
• What happens when there is a small period?

  Higher frequency and there is a greater velocity
• How do you measure velocity of sound in air?

  Make a noise 50 m from a wall and record the time that it takes for you to hear the echo then use speed = distance /time

  or

  connect two microphones to a data logger at a large distance apart then record the time difference between The sound passing between them then use speed = distance/ time
• how do you measure velocity in ripples on water surfaces?

  Use a stroboscope and measure the distance between the fixed ripples (it has the same frequency as water waves) then use v=fλ
• How are waves refracted at a boundary In terms of change of direction and speed? 


  Waves transmitted at the boundary between two materials may change direction. 

  Refraction is the change in direction of a wave at such a boundary.

  Speed decreases.
• define a period

  The time it takes for a whole wave to completely pass a single point
• What is the relationship between frequency and velocity?


  Directly proportional - as one increases so does the other
• what is the relationship between wavelength and velocity?


  as wavelength increases so does velocity
• what is the relationship between a period and frequency?


  inversely proportional - when one value increases the other decreases
• what is the relationship between period, frequency and velocity?


  smaller period = higher frequency = greater velocity
• what happens in refraction 


  • wave passes from one median to another
  • if passing into a more dense median the wave changes direction at the boundary towards the normal
• what happens as a result of refraction?


  • speed decreases
  • wavelength decreases
  • constant wave energy = constant frequency
• what happens in reflection?


  • smoother surface = stronger reflected wave (waves only reflect off of flat surfaces)
  • rough surfaces scatter the light so are matte not reflective
  • angle of incidence = angle of reflection
• What is the reflection of sound called?


  echo
• what is speculation reflection?


  reflection of a smooth and flat surface