physics - waves

• at a distance of 100m the students measured these different times

  0.43s 0.35s 0.50s 0.38

  explain why the times were different

  reaction time will be different for all students and they are all at different distances away
• describe the differences between transverse and longitudinal waves


  longitudinal waves has oscillations parallel to the direction of energy transfer

  transverse waves have oscillation perpendicular to direction of energy transfer

  there is a connection between direction of travel and oscillations
• describe motion of particles as a sound wave travels through the air 


  particles vibrate parallel to the direction of energy transfer about a fixed position
• describe how a student could determine the frequency of ripples on a lake

  • count number of waves passing a point in a specific time
  • use frequency / number of waves
• water waves are transverse waves

  give another example

  radiowave
• describe how hitting a rod causes a sound wave to travel through it 


  particles vibrate around a fixed position causing neighbouring particles to vibrate
• describe how a student could measure angle of refraction

  • mark where ray went into glass block and where it came out
  • remove block and join marks
  • use a protractor to measure angle between refracted ray and the normal
• when light crosses the boundary between air and glass it can split up the colours of the spectrum

  why is this?

  • colours have different wavelengths
  • so they travel at different speeds so refract by different amounts
• describe how a vibrating tuning fork causes a sound wave to travel through the air

  air vibrates parallel to the direction of the waves
• what colour of visible light has the longest wavelength

  red
• describe the difference between infrasound and ultrasound

  infrasound <20 Hz

  ultrasound > 20000 Hz
• explain how vibrations from earthquakes may be used to study the core of the earth

  • use of seismometers
  • waves can be refracted in the interior of the earth showing different densities
  • some seismic waves are transverse, others are longitudinal
  • transverse waves cannot pass through liquid
  • S-waves are transverse show liquid parts of earth
  • P-waves are longitudinal can go through anything
• what frequency is ultrasound

  23KHz
• Why do ultrasounds keep mice out of gardens but doesn't affect humans

  frequency is in mouse hearing range but not humans
• describe how a technician could use an ultrasound device to determine speed of ultrasound in air

  • send pulse to a wall
  • measure the distance to the wall
  • use $2 x distance/time$
• state a use of infrasound

  studying the earths structure
• state one use of ultrasound

  foetal scanning
• explain why it is difficult to predict that an earthquake will happen

  timing is so complex because we can't see what's happening deep in the earth/where the plates are rubbing
• describe how scientists may use data to see where an earthquake happened

  • find S and P wave arrival times
  • use or collect data from more than one station
  • circle drawn on map with station at centre
  • draw earthquake on that circle
  • S wave time - P wave time
  • repeat the circulation
  • the epicentre is where all circles cross at an intersection
• why is the mantle near the core hotter

  the earth is radiating heat to space
• Explain how temperature difference in the mantle causes tectonic plates to move

  • hot material rises and cold material falls so material under plate moves sideways because of uneven heating
• why do S-waves and P-waves not travel in straight lines

  change in density of rock
• explain how two different electromagnetic radiations allow someone to check a bank note 


  ultraviolet is absorbed by fluorescent substance on banknote which emits visible light into the eye
• an earthquake P-wave is a ____ wave

  infrasound
• describe how a meteor colliding with Earth could set off an earthquake


  kinetic energy of meteor may cause an earthquake

  earthquake happens when plates slide past each other

  the plates move very suddenly
• describe how ultrasound waves are used to detect fish

  • ultrasound waves go through the water and are reflected off of the fish
  • waves are received by boat
• What is the amplitude of a wave?

  This is the distance form the rest position of a wave to the crest(top) or trough (bottom).
• What is the wavelength?

  the distance between corresponding points on adjacent waves
• What is the frequency?


  number of waves that pass a point per second
• What is the period of a wave?

  The amount of time it takes for a full cycle of the wave
• What is the formula for the period?

  1/frequency
• What is a transverse wave?

  waves in which the particles vibrate in an up and down motion, perpendicular to the direction the wave is travelling
• What is a longitudinal wave?

  The wave energy moves parallel to the direction of the vibration. Particles are needed
• What is the formula for wave speed?

  wave speed = frequency x wavelength
• What is an oscilloscope?

  A device that can convert a sound signal into an electrical signal which it can display on a screen.
• How can you create water waves?

  using a signal generator attached to the dipper of a ripple tank
• What can happen to a wave at a boundary?

  absorption, transmission, reflection, refraction
• What happens when a light ray crosses from air into glass?


  - it will slow down, and bend towards the normal line
• WHat happens when a light ray crosses from glass into air?

  it will speed up, and bend away from the normal line
• What is total internal reflection?


  the complete reflection of light by the inside surface of a medium