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• What happens to waves when they change medium?

  They can change direction
• What is the change of direction of a wave at a different medium called?

  Refraction
• Where does refraction occur?


  At the boundary/interface
• What is the line at a right angle to the boundary called?

  The normal
• In what direction does the angle refract from air to glass or water?


  Towards the normal
• In what direction is the angle of refraction from glass/water to air?

  Light refracts away from the normal
• Does light travel faster in air or glass/water?

  Faster in air
• What happens when a wave is reflected?

  The wave ‘bounces’ off
• What happens when a wave is refracted?

  The wave passes into the new material but changes the direction in which it is travelling
• What happens when a wave is transmitted?


  The wave passes through the material and is not absorbed or reflected
• What happens when a wave is absorbed?


  The wave disappears as the energy it is carrying is transferred to the material
• When do echoes occur?


  When sound is reflected by a hard surface
• What is white light made up of?


  Different frequencies of light
• What is the cochlea?

  A coiled tube containing a liquid inside of the ear
• What is ultrasound?


  Sound with frequencies over 20 000 Hz
• What is sonar equipment on ships used for?

  Find the depth of the sea and to detect fish
• How can ultrasound be used for pregnancies?


  Make detailed images of unborn babies so that doctors can monitor how well the fetus is developing
• Why is gel used in an ultrasound scan?

  To stop the ultrasound from just reflecting off the skin
• What is used for an ultrasound scan to emit and receive the waves?


  A probe
• What does an ultrasound machine Do?

  Detects the time between sending the pulse out and receiving the echo, and the displays show where the echoes come from. The further down the screen, the longer the echo took to get back to the machine
• What is reflected when the ultrasound waves pass into a different medium such as fat or bone?

  Some sound
• What is infrasound?


  Sounds with a frequency less than 20Hz
• What kind of waves are P waves?

  Longitudinal
• What kind of waves are S waves?


  S waves
• How do S waves prove the earth’s liquid core?


  S waves are transverse so can only travel through solids and P waves are longitudinal so can travel through solids, liquids and gases, and during earthquakes there is always a large area of the Earth on the opposite side to the earthquake where no S waves are detected, and this is called the S wave shadow zone and this occurs because part of the interior of the earth is liquid
• How do P waves prove the Earth’s liquid core?


  There is also a P wave shadow zone, where there are a few weak P waves which arrive there, and these could only occur if waves in the liquid core had been reflected by something solid
• What is the law of reflection?


  When waves are reflected, the angle of reflection is equal to the ange of incidence