waves

• amplitude


  the height of a wave crest or trough of a transverse wave from the rest position. For oscillating motion, the amplitude is the maximum distance moved by an oscillating object from its equilibrium position

  
• compression


  squeezing together

  
• echo


  reflection of sound that can be heard

  
• electromagnetic waves


  electric and magnetic disturbances that transfer energy from one place to another

  
• frequency


  the number of wave crests passing a fixed point every second

  
• longitudinal waves


  waves in which the vibrations are parallel to the direction of energy transfer

  
• mechanical wave


  vibration that travels through a substance
• oscillate


  move to and fro about a certain position along a line
• primary seismic wave (P-wave)

  longitudinal waves that push or pull on the material that they move through as they travel through the Earth
• rarefaction


  stretched apart

  
• reflection


  the change of direction of a light ray or wave at a boundary when the ray or wave stays in the incident medium

  
• refraction


  the change of direction of a light ray when it passes across a boundary between two transparent substances (including air)

  
• secondary seismic wave (S-wave)

  transverse waves that shake the Earth side to side as they pass through
• seismic waves


  sound wave at frequency greater than 20 000 Hz (the upper frequency limit of the human ear)

  
• speed


  the speed of an object (metres per second) = distance moved by the object (metres) ÷ time taken to move the distance travelled (seconds)
• transmission/transmitted


  a wave passing through a substance
• transverse wave


  a wave where the vibration is perpendicular to the direction of energy transfer

  
• ultrasound wave


  sound wave at frequency greater than 20 000 Hz (the upper frequency limit of the human ear)

  
• vibrate


  oscillate (move to and fro) rapidly about a certain position
• wavelength


  the distance from one wave crest to the next

  
• carrier waves


  waves used to carry any type of signal
• charge-coupled device (CCD)


  an electronic device that creates an electronic signal from an optical image formed on the CCD's array of pixels
• contrast medium


  an X-ray absorbing substance used to fill a body organ so the organ can be seen on a radiograph
• electromagnetic spectrum


  the continuous spectrum of electromagnetic waves

  
• ionisation


  any process in which atoms become charged
• microwaves


  electromagnetic waves between infrared radiation and radio waves in the electromagnetic spectrum
• optical fibre


  thin glass fibre used to transmit light signals

  
• radiation dose


  amount of ionising radiation a person receives
• radio waves


  electromagnetic waves of wavelengths greater than 0.10m
• ultraviolet radiation (UV)


  electromagnetic waves between visible light and X-rays in the electromagnetic spectrum
• wave speed


  the distance travelled per second by a wave crest or trough
• white light


  light that includes all the colours of the spectrum