Waves

Waves

1. made up of a periodic motion

   • motion repeated at regular intervals
   • one complete motion known as an oscillation or a vibration
     • the source of any wave

2. produce waves

   • rope
     • fixing one end to a wall and moving the other end up and down
       • up and down movements produce vibrations or oscillations
       • rope waves travel towards wall, while rope moves up and down
     • medium through which waves move or propagate
   • ripple tank
     • small dipper moves up and down water surface
       • water particles at surface in contact with dipper moves up and down
         • motion soon spreads to other parts of water surface in tank in form of ripples
           • water molecules transfer energy to neighbouring water molecules
             • waves transfer energy
         • kinetic energy transferred to water molecules at surface
       • energy passed from dipper to water at edges of ripple tank
   • slinky
     • stretch out coiled spring on floor and fix one end of spring
       • move free end left to right
         • coil moves left and right while humps travel to other end
       • push and pull spring
         • individual coils move forward and backward
         • darks bands coils compressed travels down the spring to other end
       • wave can move from one end of spring to the other
         • energy transferred from one end of spring to the other
           • without medium being transferred

3. motion

   • transverse
     • direction of wave motion perpendicular to direction of vibration
     • light waves
   • longitudinal
     • direction of wave motion parallel to direction of vibration
     • sound waves

4. properties

   • crests and troughs
     • highest and lowest points of transverse wave
   • phase
     • any two points move in same direction, same speed and displacement from rest position
   • wavelength
     • shortest distance between any two points in wave that are in phase
   • amplitude
     • maximum displacement from rest or centre position
   • displacement-distance graph
   • displacement-time graph
     • period (T)
       • SI unit in second (s)
       • time taken to produce one complete wave
     • frequency (f)
       • SI unit in hertz (Hz)
       • f=1/T
       • number of complete waves produced per second
     • wave speed (v)
       • v=fl
         • SI unit in metre per second (m/s)
       • distance travelled by a wave per second
     • wavefront
       • imaginary line on a wave that joins all points in same phase