P12 wave properties

• waves transfer energy from one place to another without any obvious movement
• transverse waves waves travel at right angles to the direction of travel
• all electromagnetic waves travel as transverse waves
• all electromagnetic waves travel at 3x10^8 m/s in a vaccum
• longitudinal waves travel parallel to the direction of travel
• sound is a longitudinal wave
• sound waves travel at 330m/s
• compression


  waves are close together
• rare-fraction


  waves are spread further away
• electromagnetic waves

  • transverse
  • their vibrations are changed in electrical and magnetic fields at right angles to the direction of travel
• peak


  top of the wave
• trough


  bottom of the wave
• wavelength λ


  distance between identical points of a wave
• amplitude


  the distance from the midpoint of the wave to the peak or trough midpoint of the wave to the peak or trough
• period 


  the time taken for one complete wavelength
• frequency 


  the number of complete wavelengths in one second (Hz)
• reflection of a wave happens when it hits an object and bounces off it
• the reflected wave always moves away from a barrier at the same angle as the incident ray
• angle of incidence = angle of reflection
• solid line = real rays of light
• dotted line = virtual rays of light
• images produced by mirrors

  • the same size as the object
  • the same distance behind the mirror as the object is from the mirror
  • upright
  • inverted
  • virtual
• real images


  formed where light rays cross after reflection by a mirror or refraction lens. they can be cast on screen (e.g projector)
• virtual images


  are formed where light rays appear to come from. They cannot be formed by a screen (e.g mirror)
• diffuse reflection

  • rough surface
  • scattered reflected rays
• specular reflection

  • all normal rays are parallel
  • smooth surface
• absorbed waves have a heating effect
• transparent 


  light can pass through eg window
• opaque 


  light can't pass through
• translucent 


  light partially passes through
• refraction is a property of all waves
• refraction happens as a wave changes speed as it enters an object resulting in the wave bending
• sound waves are longitudinal
• the loudness of a sound increases if the amplitude increases
• your ear drum detects sound waves which make your ear drum vibrate
• humans can hear 20-20,000Hz
• sound waves convert to vibrations in solid objects
• sound waves travel through different substances at different speeds changing their wavelength but keeping their frequency the same
• sound waves can't travel through a vacuum
• an echo is a reflection of a sound wave