waves and wave movement

• Wave

  A means of transferring energy from one place to another via a travelling disturbance or oscillation
• Transverse wave

  • Direction of vibration is perpendicular to the direction in which the wave travels
• Longitudinal wave

  • Direction of vibration is parallel to the direction in which the wave travels
• examples of longitudinal waves are:

  • Sound waves in solid, liquid or gas
  • Compression waves on a spring
• Wavelength

  The distance from one point on the wave to the corresponding point on the next cycle
• Frequency

  A measure of the number of oscillations of the wave per second
• Periodic time

  The time it takes to complete one full cycle
• Amplitude

  The maximum displacement from the mean position, measured in metres
• Characteristics of a wave

  • Reflection
  • Refraction
  • Diffraction
  • Interference
• Reflection

  The bouncing of waves off an obstacle in their path
• Refraction

  The changing of direction (by the changing of speed) of a wave as it travels from one medium to another, with frequency remaining constant
• Diffraction

  The spreading of waves around a slit or an obstacle, significant when slit width is approximately the same size as the wavelength
• Interference

  The meeting of waves from two sources to produce a wave of different amplitude
• Coherent waves

  Waves with the same frequency and are in phase (or have a constant phase difference)
• Constructive interference

  Waves from two coherent sources meeting to produce a wave of greater amplitude
• Total constructive interference

  Crests of one wave over crests of another
• Destructive interference

  Waves from two coherent sources meeting to produce a wave of lower amplitude
• Total destructive interference

  Crests of one wave over troughs of another, when waves are half a wavelength out of phase
• Polarised waves

  Waves vibrating in one plane only
• Stationary/standing waves

  Formed when two periodic waves of the same frequency and amplitude travelling in opposite directions meet
• Fundamental frequency/first harmonic

  The simplest pattern of a stationary wave
• Nodes

  Locations where the amplitude is minimum
• Antinodes

  Locations where the amplitude is maximum
• Doppler effect

  The apparent change in the frequency of a wave due to the relative motion between the source and the observer
• Applications of Doppler effect

  • Police speed traps
  • Monitoring blood movement or heartbeat of a foetus
  • Weather forecasting
• to find frequency when given time

  f= 1/T
• relationship between periodic time and frequency

  T= 1/F
• distance between 2 consecutive nodes or anti nodes

  lamda/2
• distance between node and anti-node

  lamda/4