Waves (yr9)

• all sounds are waves; not all waves are sounds
• define a longitudinal wave

  oscillations of a wave parallel to the direction of movement
• define a transverse wave

  oscillations of a wave perpendicular to the direction of movement
• give 1 example of a longitudinal wave

  a sound wave
• give 1 examples of a transverse wave


  a light wave
• define the wavelength

  the distance between 2 crests
• define the frequency

  the number of waves per second
• define the amplitude

  the maximum discplacement from the zero line.
• define a time period

  the time taken to complete a wave
• write the equation for wave velocity

  $v =$$h *$$f$
• what are the 3 things a sound wave can do when it meets a boundry

  1 reflected

  2 refracted

  3 absorbed
• what is the human hearing range

  20Hz - 20kHz
• is the speed of sound greater in hot or cold air

  it is greater in hot air than cold air
• why is the speed of sound greater in hot air than cold air

  becuase, the molecules of air are moving faster and the vibrations of the sound wave can there fore be transmitted faster
• give 2 uses of sound waves

  sonar

  ultrasound
• what is sonar used for

  it measures the depths of oceans
• explain the process of sonar tech

  1 it sends waves down and records how long it takes to return

  2 then they divide it by 2 to get the distance to the bottom
• what is the equation for sonar

  speed x time/2 = distance
• explain the process of ultrasound tech

  1 the wave is sent in the body

  2 at each boundry between tissue or organs some of the ultrasound is reflected

  3 the depth of each layer is calculated using the time taken for each reflected wave to return

  4 the reflected waves are usually processed to produce a picture of the inside of the body on a screen
• why are older people's hearing worse than younger people's

  as the short hairs on the cochlea (which detect high frequencies) are worn down over time
• how does the ear drum vibrate onto the ossicles

  after the sound waves enter through the pinna and into the auditory canal which reaches the ear drum causing it to vibrate
• what are the ossicles

  hammer, anvil, stirrup
• what is the role of the ossciles

  to amplify the vibrations from the ear drum
• how do the vibrations get from the ossicles to the cochlea

  1 the vibrations are passed to the oval window (a thin membrane on the cochlea)

  2 vibrations from the oval window cause the liquid in the cochlea to vibrate
• on the cochlea: longer hairs detect lower frequencies and shorter hairs detect higher frequencies.
• how do the vibrations get from the cochlea to the brain

  1 the vibrating hairs stimulate nerve endings on the auditory nerve

  2 the auditory canal carries signals to the brain where they are interpreted as sounds
• what type of waves are electromagnetic waves

  transverse waves
• what are em waves

  transverse waves that transfer energy
• list the em spectrum from highest frequencies to lowest

  gamma, x-rays, ultra violet, visible light, infrared, microwaves, radio waves
• which is the only wave on the em spectrum humans can detect

  visible light
• what is the speed all em waves travel at in a vacuum

  $3*$$10^3 m/s$
• $1 nm =$$1 *$$10^-9 m$
• name 2 uses and dangers of radio waves

  uses:

  1 telescopes 2 satellite transmissions

  dangers:

  1 heats biological tissue 2 burns skin
• name 2 uses and 1 danger of microwaves 


  uses:

  1 microwaves 2 carries phone calls & messages

  dangers:

  1 heats up body tissue
• name 2 uses and dangers of infrared

  uses:

  1 thermal imaging 2 remotes

  dangers:

  1 heats up body 2 burns skin
• name 2 uses of visible light

  1 TVs 2 projectors
• name 2 uses and dangers of ultra violet

  uses:

  1 sterilising medical instruments 2 tanning

  dangers:

  1 effects skins cells 2 burns your skin
• name 2 uses and dangers of x-rays


  uses:

  1 x-rays 2 telescopes

  dangers:

  1 too much exposure causes damage to cells 2 cancer
• name 2 uses and 1 danger of gamma rays

  uses:

  1 sterilising medical equiptment 2 radio therapy (kills cancerous cells)

  danger:

  high exposure kills living cells
• how do you measure the velocity of ripples


  a ripple tank can calculate the frequency of the waves

  • generate ripples using a motor
  • have a light shining down on the tank and white card beneath with a ruler (to see the motion on the surface easier)